Bulletin 77 



DEPARTMENT OF THE INTERIOR 

FRANKLIN K. LANE, Secretary 

BUREAU OF MINES 

VAN. H. MANNING, Director 


I HE ELECTRIC FURNACE IN 
METALLURGICAL WORK 


BY 


DORSEY A. LYON, ROBERT M. KEENEY 

AND 

JOSEPH F. CULLEN 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 
1916 


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Bulletin 77 



DEPARTMENT OF THE INTERIOR 

FRANKLIN K. LANE, Secretary 

U.S, BUREAU OF MINES 

VAN. H. MANNING, Director 


THE ELECTRIC FURNACE IN 
METALLURGICAL WORK 

ft 06 


BY 

DORSEY A. LYON, ROBERT M. KEENEY 

AND 

JOSEPH F. CULLEN 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 
1916 




% 




k a 




The Bureau of Mines, in carrying out one of the provisions of its organic act—to 
disseminate information concerning investigations made— prints a limited free edition 
of each of its publications. 

When this edition has been exhausted, copies may be obtained at cost price only 
through the Superintendent of Documents, Government Printing Office, Washington, 
D. C., who is the authorized agent of the Federal Government for the sale of all 
publications. 

The Superintendent of Documents is not an official of the Bureau of Mines. His 

is an entirely separate office and he should be addressed: 

% 

Superintendent of Documents, 

Government Printing Office, 

Washington, D. C. 

The general law under which publications are distributed prohibits the giving 
of more than one copy of a publication to one person. Additional copies must be 
purchased from the Superintendent of Documents. The price of this publication 
is 25 cents. 


Second edition. June, 1916. 

First edition issued in October, 1914. 


D. of D. 

SEP 16 1916 


wwo'l 





CONTENTS. 


Part I. Design, construction, and operation of electric furnaces, by D. A. Lyon and 

J. F. Cullen. Page . 

Introduction. 1 

Development of use of electricity in metallurgical work... 2 

Field of the electric furnace in metallurgy. 2 

Comparison of the electric furnace and the combustion furnace. 3 

Method of producing heat in the two furnaces. 3 

Comparison of heating efficiency. 4 

Limitations to electric heating. 5 

Summary. 6 

Classification of electric furnaces. 7 

Resistor furnaces. 7 

Solid resistor furnaces. 8 

Furnaces developing heat in the charge itself. 8 

Furnaces developing heat in a core...:. 8 

Furnaces with a wall between core and charge. 9 

Furnaces without wall between core and charge. 9 

Furnaces in which the resistor is a liquid. 10 

Electrolytic furnaces. 10 

Nonelectrolytic furnaces.t. 10 

Arc furnaces. 11 

Factors governing design and construction of electric furnaces. 12 

Relation between electric energy and heat. 12 

Methods of heating with electricity. 13 

Direct heating by resistance. 13 

Induction heating. 13 

Construction of the induction furnace. 15 

Indirect-resistance heating. 15 

Arc heating. 16 

Factors affecting efficiency. 17 

Induction currents. 17 

Self-induction. 17 

Eddy currents. 18 

Hysteresis. 18 

Lag. 19 

Electromechanical forces in the induction furnace. 19 

Pinch effect. 19 

Centrifugal effect. 21 

~ factor. 21 

Measurement of power factor. 21 

Use of Ohm’s law. 22 

Power circuits. 23 

Regulation of the electric current. 24 

Electrolysis. 25 

Electrolysis of water. 25 

Electrolysis of copper sulphate. 25 

Prerequisites of an electrolyte. 26 

Essential details of electrolysis. 26 


hi 

















































IV 


CONTENTS. 


Factors governing design and construction of electric furnaces—Contd. Page. 

Mechanical construction of furnaces. 27 

Factors affecting output. 27 

Calculation of energy required. 28 

Current and voltage necessary. 29 

Proper size of interior of furnace. 29 

Proper shape of crucible. 30 

Types of furnace linings. 30 

Acid refractories. 30 

Silica. 30 

Dinas brick. 30 

Canister. 31 

Fire clay. 31 

Basic materials. 32 

Lime. 32 

Magnesia. 32 

Electrically calcined magnesite. 32 

Bauxite. 32 

Neutral linings.'. 33 

Carbon. 33 

Chromite... 34 

Alundum. 34 

Carborundum.- . 35 

Crystolon. 35 

Suitable refractories. 36 

Melting points of refractory materials.,. 37 

Proper thickness of furnace walls. 38 

Heat conductivities of furnace-wall materials. 38 

Proper volume of crucible. 39 

Insulation desirable. 39 

Electrodes. 41 

Manufacture of electrodes. 42 

Carbon compared with graphite electrodes. 42 

Energy loss in electrodes. 42 

Efficiency of electrodes. 43 

Conductivity of electrodes. 43 

Essentials in use and design of furnace electrodes. 43 

Wattage as a measure of flow of heat. 44 

Formulas. 45 

Determination of proper size of electrodes. 45 

Proper construction of electrode holders. 47 

Heat sockets and clamps. 47 

Top holders. 47 

Side holders. 48 

Essential details of holders. 48 

Specially shaped electrodes. 49 

Types of top holders. 50 

Movable side holders. 55 

Metallic conductors in electrode heads. 57 

Electrode dimensions and electrode bundles. 60 

Joining of electrodes..•. 65 

Electrical loss at joints. 66 
























































CONTENTS. V 

Page. 

Cost of electric power. 57 

Hydroelectric power. 67 

Power produced by gas engines and steam turbines. 68 

Operating conditions of electric furnaces. 70 

Conclusion. 71 

Part II. The smelting of metals in the electric furnace, by D. A. Lyon and 

Pv. M Keeney. 

Introduction. 72 

Aluminum. 72 

Introduction. 72 

Prerequisites for the production of aluminum by present methods. 73 

Processes for purifying bauxite. 73 

Hall process for producing aluminum. 74 

Heroult process for the manufacture of aluminum. 75 

Serpek process. 76 

Present status of aluminum manufacture in the United States. 77 

Factors governing growth of aluminum industry. 78 

New sources of alumina..-. 78 

Processes for producing aluminum from ores other than oxides. 79 

Tone’s method. 79 

Bett’s process. 80 

Iron. 81 

Present status of electric furnace in smelting iron ores. 81 

Use of coke and charcoal. 81 

Possible use of crude oil as a reducing agent. 84 

Use of electric iron reduction furnace at present. 84 

Engineers’ report of the experimental work at Trollliattan. 85 

Quality of pig iron produced in electric furnace. 85 

Value of gas produced. 86 

Copper. 87 

Present status of the electric smelting of copper ores. 87 

Experimental work of Vattier, Schilowski, Wolkoff, and others. 87 

Summary. 88 

Lead ores and complex sulphide ores..'. 89 

Gold and silver ores. 96 

Zinc. 91 

Present methods of zinc smelting. 9i 

Zinc smelting in the electric furnace. 92 

Electric zinc smelting at Trollhattan and Sarpsborg. 93 

Equipment at the two plants. 93 

Smelting process. 93 

Results of operation of furnaces. 94 

Comments by Harbord and Moulden. 95 

Experiments at McGill University. 96 

Experiments of Johnson. 97 

Electric smelting of zinc sulphide ores with iron as a desulphurizing agent.. 97 

Present status of electric zinc smelting. 98 

Difficulty of condensing zinc vapor into metal. 99 

The electrode problem. 99 

Retort and electrode consumption. 99 

The fundamental difficulty. 100 

Tin. 101 



















































VI 


CONTENTS. 


Part III. The manufacture of ferro-alloys in the electric furnace by R. M. 

Keeney. rage . 

Introduction. 102 

Early development of the manufacture of ferro-alloys. 103 

Development previous to the use of the electric furnace. 103 

Introduction of the electric furnace. 104 

Present status of the manufacture of ferro-alloys in the electric furnace. 105 

Types of electric furnaces used in ferro-alloy manufacture. 10G 

Ferrosilicon furnace of the Siemens type. 10G 

Keller furnace. 108 

Chaplet furnace. 109 

Girod resistance crucible furnace. 109 

Girod arc furnace. 110 

Meraker furnace. Ill 

Series furnace. 112 

Ilelfenstein furnace. 113 

General construction of electric ferro-alloy furnaces. 113 

Fundamental parts. 113 

Construction and life of linings. 115 

Electrode holders.'. 115 

Types. 115 

Waste of heat in open-top furnaces. 11G 

Character of electric current. 117 

Some European electric-furnace ferro-alloy plants. 118 

Keller. Leleux & Co., Livet, Isere, France.•. 118 

Power supply. 118 

General plan of the works and furnaces. 119 

Products. 119 

Societe Electro-Metallurgique Proc^des Paul Girod, Ugine, Savoie, France. 120 

Power supply. 120 

General plan of the works. 121 

Production. 122 

Meraker Electric Smelting Co. 122 

Power supply. 123 

General plan of works and furnaces. 123 

Products..•. 124 

Ferro-aluminum. 125 

Ferroboron. 125 

Ferrochrome. 127 

History. 127 

Work of experimenters. 127 

Neumann. 127 

Moissan._ 128 

Experimental smelting of chromite in the electric furnace. 128 

Construction of furnace used. 128 

Materials used in charge. 128 

Results obtained. 129 

Theory of chromite smelting. ]31 

Reduction with carbon. 131 

Reduction with silicon and other reducing agents. 133 

Refining of ferrochrome. 134 

Manufacture of ferrochrome. 135 

Ores and raw materials used. 135 

Types of furnaces used. 13 g 

Process of manufacture. 13 g 






















































CONTENTS. 


VII 


Ferrochrome—Continued. p age> 

Manufacture of—Continued. 

Power and electrode consumption. 138 

Cost of manufacture of ferrochrome.'. 139 

Selling prices of ferrochrome. 140 

Uses of ferrochrome. 140 

Ferromanganese. 141 

History. 141 

Experiments in the production of ferromanganese. 142 

Theory of production. 142 

Process of manufacture. 143 

Uses of ferromanganese. 144 

Ferromanganese-silicon. 145 

Electric smelting of molybdenite and the production of ferromolybdenum. 146 

History.■_ 146 

Investigators. 146 

Guichard. 147 

Lehner. 147 

Neumann. 147 

Experiments on reduction of molybdenite. 148 

Theory. 149 

V 

Process of manufacture. 150 

Uses. 150 

Ferronickel. 151 

Experiments on the production of natural alloys of nickel directly from ore 

in the electric furnace. 151 

Experiments at Sault Ste. Marie. 151 

Experiments at plant in North Carolina. 153 

Experiments of Stephan. 153 

Ferrophosphorus. 154 

Ferrosilicon. 154 

History. 154 

Theory. 155 

Silicides of iron. 155 

Properties of ferrosilicon. 158 

Disintegration and evolution of gas from ferrosilicon. 160 

Reduction with carbon. 161 

Production from iron ore of ferrosilicon containing 30 per cent silicon. 162 

Production of ferrosilicon containing 30 per cent silicon from iron turnings.. 163 

Fifty per cent ferrosilicon. 163 

Manufacture of ferrosilicon in the blast furnace. 163 

Manufacture of ferrosilicon in the electric furnace. 164 

Raw materials used. 164 

Character of ferrosilicon plants. 166 

Practice. 167 

Method of charging. 167 

Tapping. 169 

Changing electrodes. 169 

Slag formation. 170 

Results of early operations. 170 

Power consumption. 171 

Workmen required. 171 

Products. 172 

Packing and transportation of ferrosilicon. 172 

Cost of manufacture. 173 

Uses. 174 






















































VIII 


ILLUSTRATIONS. 


Page. 

Alloys of iron and silicon with other elements. 175 

Ferro titanium. 175 

Electric smelting of tungsten ores and the production of ferrotungsten. 177 

History. 177 

Experiments of Stassano. 178 

Experiments with Colorado ferberite. 178 

Conclusions. 180 

Theory of tungsten alloys. 180 

Reactions. 181 

Process of manufacture. 182 

Uses. 184 

Electric smelting of vanadium ores and the production of ferrovanadium. 184 

Glossary... 186 

Selected bibliography. 190 

Publications on metallurgy and mineral technology. 208 


ILLUSTRATIONS. 


Page. 

Figure 1 . Acheson graphite furnace. 8 

2. Cross section of electrically heated tube furnace. 9 

3. Acheson carborundum furnace.. 9 

4. Heroult 2.5 ton, single-phase steel furnace. 10 

5. Stassano furnace. 11 

6. Cross section of Siemens vertical-arc heating furnace. 12 

7. Curve representing a complete wave or cycle of alternating current.. 13 

8. A magnetic field, in which a conductor has been placed. 14 

9. Cross section of Girod furnace... 16 

10. Cross section of Helberger furnace. 16 

11. Cross section of Moissan furnace (after Stansfield). 17 

12. Cross section of the bath of an induction furnace, showing effect on 

surface of bath of the resultant of the different forces acting. 19 

13. Different types of electric furnace connections. 24 

14. Trollhattan electrode before and after use. 47 

15. Specially shaped electrodes for electric furnaces. 49 

16. Holder formerly used with carbide furnaces. 50 

17. Electrode holder with cooling device. 51 

18. Electrode holder with another type of cooling device. 52 

19. Detailed views of electrode holder satisfactorily used in carbide 

furnaces. 53 

20. Another type of electrode holder satisfactorily used in carbide fur¬ 

naces. 54 

21. Water-cooled electrode holder.. 55 

22. Holder for round electrode.. 56 

23. Electrode holder cooled with water under pressure. 57 

24. Electrode holder used in Germany. 58 

25. Electrode holder with movable contact. 59 

26. Holder for a block electrode. 60 

27. Modification of holder for block electrode. 61 













































ILLUSTRATIONS. IX 

Page. 

Figure 28. Electrode holder used by the Aktisbolaget Elektrometall Ludwika. 62 

29. Electrode holder used by Nathusius. 63 

30. Electrode with iron connection in top. 63 

31. Screw-bolt electrode connection. 63 

32. Combination of four screw-bolt electrodes. 64 

33. Electrode connection used by Lessing. 64 

34. Electrode connection used by Keller. 64 

35. Electrode holder used in Stassano furnace. 65 

36. Three types of electrode joints. 66 

37. Aluminum furnace. 75 

38. Plan and elevation of Siemens type of ferrosilicon furnace. 106 

39. Electrodes and holders used in Siemens type of ferrosilicon furnace. 107 

40. Keller ferro-alloy furnace. 108 

41. Plan and elevation of Chaplet ferro-alloy furnace. 109 

42. Plan and elevation of Girod resistance furnace. 110 

43. Plan and elevation of Girod electrode ferro-alloy furnace. 110 

44. Plan and elevation of ferrochrome furnace at Kopperaaen, Norway. Ill 

45. Norwegian and Italian electrodes and holders. Ill 

46. Plan and elevation of single-phase series ferro-alloy furnace. 112 

47. Elevations of three-phase series ferro-alloy furnace. 113 

48. Elevation of Helfenstein furnace. 114 

49. System of electrical connections for several small furnaces. 114 

50. Delta connections of three single-phase furnaces. 117 

51. Electrical connections of a three-phase furnace. 118 

52. Plan of Girod ferro-alloy plant. . 121 

53. Cooling curves of the iron silicon system. 157 

54. Specific gravity curves of ferrosilicon samples containing varying 

percentages of ferrosilicon. 159 

55. Plan of ferrosilicon plant designed by Conrad and Pick. 167 

56. Elevation of Conrad and Pick’s ferrosilicon plant. 168 
































THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


By Dorsey A. Lyon, Robert M. Keeney, and Joseph F. Cullen 


PART I. DESIGN, CONSTRUCTION, AND OPERATION OF 

ELECTRIC FURNACES. 

By Dorsey A. Lyon and Joseph F. Cullen. 


INTRODUCTION. 

In connection with its investigation looking to the prevention of 
waste and the increase of safety and efficiency in the mineral indus¬ 
tries the Bureau of Mines has undertaken a study of the possible uses 
of the electric furnace in metallurgy. This bulletin presents a com¬ 
pilation of such data as seem to be useful for the information of 
persons who may be interested in the matter. In the application of 
electricity to metallurgy three kinds of processes are involved, namely, 
mechanical, thermal, and electrolytic. 

Under the mechanical application of electricity come those proc¬ 
esses of dressing and concentrating ores that are known as either 
electrostatic or electromagnetic processes. 

In electrothermic processes the current is used as a source of heat. 
The fundamental differences between the various types of electric 
furnace that are at present in commercial use relate to the manner in 
which the electric current is applied, as may be noted by reference to 
that part of this report in which the subject is discussed. 

In electrolytic processes the electric current is used for depositing 
metals from solutions. The process may be conducted in one of the 
following ways: (1) The material to be treated may be put into solu¬ 
tion and then electrolyzed, the material thus treated forming the 
electrolyte; (2) the material to be treated may form the anode or be 
placed in contact with the anode; or (3) the material to be treated 
may form the cathode or be placed in contact with the cathode. 

This report treats of electrothermic processes, with the possible 
exception of those for the reduction of aluminum from its ores. 
Moreover, of the processes used in the so-called electrochemical in¬ 
dustries only those for the reduction of an ore to metal, or to a com¬ 
pound of the metal that is of value in itself, or is an aid in metallurgical 
work, are here discussed. 





2 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

DEVELOPMENT OF USE OF ELECTRICITY IN METAL¬ 
LURGICAL WORK. 

The use of electricity as a source of heat in metallurgical work is 
comparatively recent. Although many chemists and metallurgists 
had previously conducted small experiments, Siemens, in 1882, was 
probably the first to make use of it in metallurgical work for commer¬ 
cial purposes . a Then came the furnace of E. H. and A. H. Cowles/ 
who in 1885 invented a furnace for the production of aluminum alloys 
and for a variety of other purposes. A year later Paul Heroult 0 and 
C. M. Hall d patented processes for the production of aluminum. In 
1893 Wilson/ aided by data gathered by Moissan in his classical 
experiments, developed the calcium-carbide furnace, which was 
followed in 1896 bv Achesoifs carborundum furnace/ Two vears 
later Captain Stassano of Italy patented an electric furnace 0 for 
smelting iron ores, and the following year demonstrated the working 
of his process. In 1900 the production of ferro-alloys in the electric 
furnace was begun, and at the present time practically all ferro-alloys 
are made in electrically heated furnaces. 

As a result of the work of Stassano and of the successful making of 
ferro-alloys in the electric furnace, steel was next made in France by 
Heroult and in Sweden by Kjellin under patents taken out in 1900. 
In 1906 experiments on the reduction of iron ores in the electric fur¬ 
nace were conducted by the Canadian Government and by Gronwall, 
Lindblad, and Stalhane in Sweden. The production of pig iron in the 
electric furnace in Sweden at the present time is a direct result of the 
work of the three men last mentioned. 

In the development of the electric furnace its uses have been 
extended, and to-day it is used not only in metallurgy but in many 
branches of applied chemistry as well. 

FIELD OF THE ELECTRIC FURNACE IN METALLURGY. 

The electric furnace is not necessarily a competitor of the com¬ 
bustion furnace, for it has won its position in the industrial world 
chiefly through the fact that it permits the use of a higher tempera¬ 
ture than can be attained with the combustion furnace. This is 
why, for example, high-grade ferrosilicon and many of the ferro-alloys 
are not produced in the combustion furnace. Again, the electric 
furnace is particularly suited to the production of those elements that 

a Siemens, William, and Huntingdon, —, Report of 52d meeting: British Assoc. Adv. Science, August, 
1882, pp. 496-4^8. 

b U. S. patent 319795 (1884). 

c French patents 175711, April 23, 1886; and 170003, April 15, 1887. 

d U. S. patents 400766 and 400664, April 2,1889 (applied for July 9,1886). 

< Wilson, T. L., Industries and Iron, vol. 20,1896, p. 322. 

/ Fitzgerald, F. A. J., The carborundum furnace: Electrochem. Ind., vol. 4, 1906, p. 53. 

g Electrochem. and Met., vol. 1,1901, p. 230; Electrochem. Ind., vol. 1, 1902-3, pp. 247-303. 




THE ELECTRIC FURNACE AND THE COMBUSTION FURNACE. 3 

may themselves constitute the walls of the furnace, so that it is 
possible to effect a great saving in crucibles and retorts, the cost of 
which was a large item in older methods. As the best illustration 
of such products, phosphorus and carbon bisulphide may be cited. 

In short, the advent of the electric furnace into metallurgy has 
made possible developments that were not possible through the use 
ol the combustion furnace. For example, such substances as mag¬ 
nesia, lime, and molybdenum were formerly considered infusible, but 
at the high temperature attained in the electric furnace these sub¬ 
stances are not only melted but may be volatilized. New processes 
based on this development have been perfected for the purification 
and separation of substances, and metals and their combinations 
may be separated by fractional distillation in the same general way 
as substances having comparatively low boiling and volatilizing 
points. 

It is perhaps true that some metallurgists have unduly emphasized 
the importance of the electric furnace in metallurgical work, and for 
that reason it may be well briefly to consider a few of the fundamental 
facts regarding the possibilities of the use of high temperatures. 

In the first place, it is thought that any known oxide can be 
reduced by carbon within the range of temperature possible in the 
electric furnace. At any rate, it is easy in such a furnace to reduce 
such stable oxides as those of calcium, silicon, and magnesium, and 
to produce carbides of these elements as well as those of boron, 
aluminum, molybdenum, tungsten, and titanium. These carbides 
are extremely stable, resisting not only attacks of water, but also 
most of the active chemical agents. 

The writers have purposely emphasized the fact that the electric 
furnace is not a competitor of the combustion furnace, but has its 
own particular field of usefulness. However, quite possibly it may 
in time become a competitor of the combustion furnace for certain 
work, and, in fact, it already is to some extent. 

COMPARISON OF THE ELECTRIC FURNACE AND THE 

COMBUSTION FURNACE. 

METHOD OF PRODUCING HEAT IN THE TWO FURNACES. 

As is well known, in the combustion furnace heat is produced by 
the oxidation of some combustible substance, the product of com¬ 
bustion being a gas. The efficiency attained, or the ratio between 
the amount of heat usefully employed in the furnace and the heat 
value of the fuel or electric energy supplied, is generally rather low, 
a fair average being probably about 25 per cent. On the other 
hand, the source of heat in an electric furnace is electrical energy, and 
it is perhaps fair to assume that the average efficiency of such a 


4 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


furnace is 60 per cent, whereas in the combustion furnace it is per¬ 
haps never more than 66 per cent, as shown in the following tables: 


Average thermal efficiency of various types of combustion furnaces. 


Type of furnace. 

Product. 

Thermal 

efficiency.® 

Blast. 

Cast iron. 

Per cent. 

52 to 66- 

Acid process. 

Steel. 

11.9 

Basic process. 

.do. 

10.0 

Reverberatory. 

Pig iron. 

8.5 

Do_ . 

Wrought iron. 

5 

Siemens crucible. 

Steel. 

4 

Greenwood crucible. 

.do. 

2 

Retort. 

Zinc. 

2 to 3 




a Average efficiency for steam, 50 to 60 per cent. 


Average thermal efficiency of three types of electric furnace. 


Type of furnace. 

Product. 

Horse¬ 

power. 

Tempera¬ 

ture. 

Thermal 

efficiency. 

Aeheson. 

Graphite. 

1,000 

200 

° C. 
3,300 

Per cen f . 

Jacobs. 

Fused AGO:;. 


74 

Aeheson_... 

Carborundum. 

1,000 

3,000 

76.5 




COMPARISON OF HEATING EFFICIENCY. 

Some idea as to the heating value of electrical energy as compared 
to that of coal may be obtained from the following discussion of 
“Electric heat versus heat from fuel. 7 ’ a 

One kilowatt-hour & is equivalent to 860 kilogram-calories, which is approximately 
the full heat obtained from 100 grams of good coal when completely burned to carbon 
dioxide. If the cost of a ton of coal of 2,000 pounds (907 kg.) is a dollars, and if the 
efficiency of heat production by burning coal is x per cent, then the coal required for 
producing 860 kilogram-calories costs a divided by 90.7 x dollars. On the other hand, 
if the cost of 1 kilowatt-hour is b cents and if the efficiency of producing heat from elec¬ 
trical energy is y per cent, then the kilowatt-hours required for producing 860 kilogram- 
calories cost b divided by y dollars. Hence electrical heat will be cheaper than heat 
produced by combustion of fuel if a y is greater than 90.7 b x. To go further, we need 
the efficiency figures x and y. By assuming definite figures we introduce, of course, 
an uncertainty into our comparison, but it will probably be considered fair if, for a 
first approximation, we assume a 25 per cent efficiency for fuel heating and a 75 per 
cent efficiency for the electric furnace. Then we conclude that electrical heat will 
be cheaper than heat produced from fuel if a is greater than 30.2 6, or, in other words, 
if the cost of a ton of coal in dollars is more than 30 times the cost of a kilowatt-hour in 
cents. For instance, to compete with coal at $6 per ton, the electric kilowatt-hour 
would have to cost less than 0.2 cent. This is clear evidence that if the electric furnace 
did not have other important features it would not compete with fuel heat under 
ordinary conditions. 


a Electrochem. and Met. Ind., vol. 5, 1907, p. 298. 


i> For definition of electrical units, see p. 186. 


















































THE ELECTRIC FURNACE AND THE COMBUSTION FURNACE. 5 

We have purposely made this comparison on the basis of the ton of coal and of the 
kilowatt-hour, although it has become customary to use the electric horsepower-year 
as the unit of electrical energy in such estimates. Then the above condition can be 
stated in this way: Electric heat will be cheaper than fuel heat if the cost of 1 ton of 
coal is more than one-half of the cost of the electric horsepower-year. Stated in this 
form, the comparison looks more favorable for the electric furnace than when stated 
as in the preceding paragraph. But in reality it is not proper to make the comparison 
on the basis of a horsepower-year, since we thereby implicitly assume that the electric 
furnace is working continuously every hour all year round, which is in general a 
decidedly improper assumption. 

It is, of course, clear that the above comparison is exceedingly narrow in that 
it considers only one single side of the problem, namely, the amount of fuel and 
electrical energy required to produce the same number of calories. But even in 
this very respect the above comparison falls short of the truth and does not do 
justice to the electric furnace. The chief reason is that electrical heating is essen¬ 
tially internal heating, permitting a very high concentration of energy at any point 
wanted and thus enabling one to produce high temperatures. Fuel heating, on the 
other hand, is always more or less transmission of heat from the fuel to the charge, and 
the rate of heat transmission depends on the difference of the two temperatures; this 
rate decreases rapidly the higher we go up in the temperature. Naturally with fuel 
heating we can never obtain any higher temperature than that of the burning fuel 
itself. There is no corresponding limitation in electric heating. This is the funda¬ 
mental reason why for all very high temperature processes the electric furnace reigns 
supreme. 

LIMITATIONS TO ELECTRIC HEATING. 

It is necessary to qualify the statement that there is no limitation 
to electric heating. Theoretically there is not, but practically there 
is, for the following reasons: As an electric current passes through a 
conducting medium heat is produced. The intensity of this heat 
depends on the amount of current that passes, and as most substances 
are conductors when hot, the degree of intensity possible is theoret¬ 
ically unlimited. In practice, however, the conducting substance 
begins to fuse when heated to its melting point, and one is then con¬ 
fronted with the physical difficulty of keeping the conducting medium 
in place. Or if this be accomplished, the conducting medium ulti¬ 
mately vaporizes, the gaseous materials escape, and heat is thus 
carried away from the furnace as rapidly as it is supplied. The tem¬ 
perature of the electric arc, which is somewhere between 3,600° and 
4,000° C., is perhaps the highest temperature attainable at present. 

Theoretically it is possible to obtain by the combustion of carbon 
in oxygen a higher temperature than can be attained in the electric 
furnace. In practice, however, the attainment of such temperature 
is impossible for the following reasons: 

1. At high temperatures carbon oxidizes to CO and not to C0 2 . 
The oxidation of 1 pound of carbon to C0 2 generates 8,100 pound- 
calories, whereas the oxidation of 1 pound of carbon to CO generates 
only 2,430 pound-calories. 


6 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


2. The gaseous products formed escape rapidly and carry heat 
away from the furnace. 

3. In commercial work, at present at least, it is not feasible to 
supply pure oxygen for combustion purposes. 

4. Atmospheric oxygen is accompanied by four times its volume 
of nitrogen, so that when air is used instead of pure oxygen the nitro¬ 
gen is raised to a high temperature and carries from the furnace the 
heat it has absorbed. 

SUMMARY. 

The foregoing paragraphs may be briefly summarized, as in the 
following sentences: 

In the combustion furnace, no matter what form of fuel is used, the 
temperature can not exceed 2,000° C. 

In the combustion furnace the efficiency varies from 2 per cent to 
60 per cent, whereas in the electric furnace it averages about 60 per 
cent. 

In the combustion furnace not only is it necessary to take care of 
the products of combustion, but these products may reduce the effi¬ 
ciency of the process, whereas the electric furnace is free from these 
difficulties. 

In the electric furnace the temperature attainable is the same 
whether the furnace is operated on a commercial or on a laboratory 
scale. 

In the electric furnace, the heat may be developed at any desired 
point, and by passing the current through the substance that is to be 
treated the heat necessary for the operation may be developed within 
the substance itself. 

The temperature of an electric furnace is under absolute control. 

Any atmosphere desired—that is, neutral, oxidizing, or reducing— 
may be obtained within the electric furnace. This feature, together 
with the fact that the product is generally much purer than that of 
the combustion furnace, is a great factor in favor of the electric 
furnace. 

In general, one may say that it is necessary to use an electric fur¬ 
nace in all operations requiring a temperature higher than 2,000° C.; 
for work requiring a temperature of less than 2,000° C., local condi¬ 
tions and the nature of the work to be done will affect the choice of 
the electric or the combustion furnace. As has been previously 
pointed out, the cost of power will largely enter into the matter, but 
even with a high cost of electric power, the superior efficiency of the 
electric furnace, the possibility of obtaining a purer product, and 
perhaps greater safety for the workmen—any or all of these factors 
may lead to a decision in favor of the electric furnace. 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. ? 

CLASSIFICATION OF ELECTRIC FURNACES. 

Electric furnaces may be classified in a more or less arbitrary 
manner, and different authorities have used sucli classifications as 
seemed most desirable. Stansfield’s classification a is substantially 
as follows: 

I. Arc furnaces: 

A. Those with independent arc (Moissan furnace). 

B. Those with direct-heating arc (Siemens vertical-arc furnace). 

II. Resistance furnaces: 

A. Those with special resistor— 

1. Furnaces in which charge constitutes the resistance (carborundum 
furnace). 

2. Furnaces having resistor in walls (electrical tube furnace). 

B. Those without special resistor— 

1. Furnaces in which electrolysis is not employed (charge constitutes the 
resistance): 

(a) Those in which the charge is not melted, but remains in a solid 
condition (graphite furnaces). 

( b) Those in which charge is added in solid condition but subsequently 
becomes liquid (Heroult ore-smelting furnaces). 

(c) Those in which charge is added in liquid condition (Kjellin 
steel furnaces). 

2. Electrolytic furnaces (furnaces for producing aluminum). 

Burgess 6 cdassifies electric furnaces according to the character 
of the medium constituting the conductor, as follows: 

I. Furnaces in which the heat is developed by the passage of current through a 
solid conducting medium or “resistor.” 

A. The conducting medium, or core, may consist of the material that is to un¬ 
dergo useful transformation. 

B. The heat is developed in a core of conducting material and this heat in turn 
is communicated to the surrounding material that constitutes the charge, either 
with or without a wall between the two cores and the charge. 

II. Furnaces in which the heat is developed by the passage of current through a 
solid or liquid conducting medium. 

A. Electrolytic. 

B. Nonelectrolytic. 

III. Furnaces in which the heat is developed by the passage of current through a 
gaseous conducting medium. 

A. Arc furnaces. 

(1) In which an arc plays between two or more electrodes in the neigh¬ 
borhood of material to be treated. 

(2) In which an arc is maintained between one carbon electrode and the 
material to be treated, the latter acting as a second electrode. 

RESISTOR FURNACES. 

A resistor signifies a substance that is used as a medium for devel¬ 
oping heat when electric current is passed through it. As stated by 
Burgess in his classification of electric furnaces, a resistor may be 

a Stansfield, A., The electric furnace, its evolution, theory, and practice, 1907, p. 32. 
b Burgess, C. F., The present status of electric furnace working: Jour. Western Soc. Engrs., vol. 10, 
1905, p. 107. 

44713°—Bull. 77—16-2 





8 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

either a solid, a liquid, or a gas. Materials commonly used for this 
purpose are the metals, carbon, and substances that are not conduc¬ 
tors at ordinary temperatures, but become conductors when hot. 
When such substances are used, it is necessary first to heat them by 
some auxiliary means. The construction of a resistance furnace is 
based upon the fact that by resistance an electric current is trans¬ 
formed into heat.® 

SOLID RESISTOR FURNACES. 

FURNACES DEVELOPING HEAT IN THE CHARGE ITSELF. 

Furnaces in which the heat is developed by passage of the current 
through a solid conducting medium are described below. 

An illustration of the type of furnace in which the conducting 
medium, or core, may consist of the material that constitutes the 
charge is the Acheson graphite furnace, shown in figure l. 6 In this 
furnace a core, c, of carbon rods is needed to carry the current until 



Figure 1.—Acheson graphite furnace. 

the charge becomes heated. The base, b, and end walls, aa, which 
support the electrodes, are permanent, but the side walls, dd, are 
not, and can be pulled down after a run. The electrodes comprise 
a number of graphite rods, e, which are set in a block of carbon as 
shown in the figure; electric contact being made by a terminal plate, 
which may be water-cooled. In making graphite in a furnace of this 
kind a charge of anthracite coal, g, is placed around the core of carbon 
rods, c, and then covered with a layer of material that is a poor con¬ 
ductor of both heat and electricity. When the current is turned on, 
it passes through the core of carbon rods and heats the anthracite, 
which is gradually converted into graphite by the high temperature 
attained. The electrical resistance of the graphite is very low, and 
for that reason the current has little tendency to pass through the 
outer parts of the charge. 

FURNACES DEVELOPING HEAT IN A CORE. 

That type of furnace in which the heat is developed in a core of 
conducting material, this heat being in turn communicated to the 
surrounding material that constitutes the charge, may or may not 
have a wall separating the core from the charge. 


a For laws of electrical resistance, see p. 187. 


b Stansfield, A., The electric furnace, 1907. p. 145. 
















































CLASSIFICATION OF ELECTRIC FURNACES. 


9 


FURNACES WITH A WALL BETWEEN CORE AND CHARGE. 

I he electrically heated tube furnace (fig. 2) is an example of the 
type of furnace having a wall between the core and charge. As is 
shown in the figure, it is constructed by winding a wire, r, which 
forms the resistor, around a tube, t, which is made of porcelain or 
some other highly refractory substance. The resistor wire may be 
of either platinum 
or an alloy, such 
as nickel and chro- 


perature. In some 
furnaces of this 
type, the resistor 

Figure 2.— Cross section of electrically heated tube furnace. 

wire, instead of 

being wound around a tube, is embedded in the inner surface of 
the refractory envelope, e. In the operation of the tube furnace the 
charge is placed in the tube, the leads a and b are connected to an 
electric circuit and, by means of a controlling rheostat, enough 
current is supplied to the resistor wire to overload it, so to speak, 
and the resistance that the current meets transforms the electric 
energy into heat. By varying the intensity of the current it is pos¬ 
sible to obtain any desired temperature below the melting point of 
the wire, which for platinum is 1775° C. or 3227° F. 


mium, that has a 
high fusing tern- • 



FURNACES WITHOUT WALL BETWEEN CORE AND CHARGE. 


The Acheson carborundum furnace,® shown in figure 3, is an ex¬ 
ample of the type of furnace in which there is direct contact between 
the core and the charge. 



Figure 3.—Acheson carborundum furnace. 

The end walls act are permanent, and support the heavy bronze 
electrode holders f and g. Inserted into these holders are large bun¬ 
dles of carbon rods, c and d, and between the rods is a core of broken 
carbon which remains until the end of the operation. Around this 
core is placed a mixture consisting approximately of 34.2 per cent 
coke, 54 per cent sand, 9.9 per cent sawdust, and 1 per cent salt. 


a Fitzgerald, F. A. J., The carborundum furnace, Electrochem. Ind., vol. 4, 1906, p. 53. 





















































































10 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

The broken carbon core acts as the resistor. When a current is 
passed through this core it becomes heated and in turn heats the 
surrounding charge, which then becomes a conductor and acts as a 
resistor itself. 

FURNACES IN WHICH THE RESISTOR IS A LIQUID. 

Furnaces in which heat is developed by the passage of a current 
through a liquid conducting medium are of two types, electrolytic 
and nonelectrolytic, to use terms already defined. 




Figure 4.— Heroult 2.5-ton, single-phaso steel furnace. 

ELECTROLYTIC FURNACES. 

The furnaces in which aluminum is made by the Heroult and Hall 
processes are the best examples of the electrolytic type of furnace. 
Inasmuch as their construction is described in the second part of 
this bulletin, a description is not necessary here. 

NONELECTROLYTIC FURNACES. 

The Heroult steel furnace (fig. 4) is illustrative of the nonelectro- 
lytic type of furnace. In this furnace the molten steel is covered 
with a layer of slag. The heat in the furnace is generated by the 
passage of the electric (alternating) current between the electrodes 
through the liquid layers of slag and metal. 








































































































CLASSIFICATION OF ELECTRIC FURNACES. 


11 


ARC FURNACES. 

Arc furnaces may be classified, according to the method used in 
forming the arc, in two general types: (1) Furnaces in which the arc 
plays between two or more electrodes in the neighborhood of the 



Figure 5.—Stassano furnace. 


material to be treated, and (2) furnaces in which the arc is main¬ 
tained between one carbon electrode and the charge, the latter act¬ 
ing as a second electrode. 

The Stassano furnace (fig. 5) is a good illustration of the first 
type. An arc is maintained between the ends of two electrodes, and 









































































12 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


in this way the metal and slag are heated by the heat radiated from 
the arc. 

The Siemens vertical-arc heating furnace, as shown in figure 6, is 
a furnace of the second type. In this furnace the charge d, which is 
in contact with the lower electrode c, is heated by maintaining an 
arc between the end of the upper electrode b and the charge d. 

FACTORS GOVERNING DESIGN AND CONSTRUCTION 

OF ELECTRIC FURNACES. 

Naturally, in the design and construction of an electric furnace, 
the aim is to obtain in the operation of the furnace the highest effi¬ 
ciency compatible with the oper¬ 
ating conditions. Some of the 
factors that govern the efficiency 

of an electric furnace are brieflv 

%) 

considered below. 

RELATION BETWEEN ELECTRIC 
ENERGY AND HEAT. 

The measure of the electric 
power supplied to the electric fur¬ 
nace is the watt. If 1,000 watts 
be used for one hour, one kilo¬ 
watt-hour has been used. The 
expenditure of this much energy 
is equivalent to 8G0 kilogram- 
calories, which represents the full 
amount of heat to be expected 
from the complete combustion 
(to carbon dioxide) of 100 grams 
of good coal. By calculation 
it is possible to determine the 
amount of heat or the tempera¬ 
ture necessary to bring about the 
results desired in any metallur¬ 
gical process. To attain and maintain this temperature a certain 
rate of heating is necessary, this rate depending on the rate at which 
the heat is conducted away through the furnace walls, the dimen¬ 
sions of the furnace, and the cooling effect of the charge that is 
added from time to time. When, as in the electric furnace, this 
heat is to be supplied by electrical energy, the first consideration is 
so to construct the furnace as to obtain the largest practicable per¬ 
centage of heat value from the electrical energy supplied. In order 
to do this, the designer must have, of course, a clear understanding 



Figure 6.—Cross section of Siemens vertical-arc 
heating furnace. 



































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


13 


of the fundamental laws of electricity a and the heating effects of the 
electric current. The different methods of heating may be briefly 
stated as follows: Direct heating by resistance; induction heating; 
indirect resistance heating; and arc heating. The methods are 
briefly described below. 

METHODS OF HEATING WITH ELECTRICITY. 

DIRECT HEATING BY RESISTANCE. 

An illustration of direct heating by resistance is the heating of a 
metal bar or wire by passing an electric current through it. The 
metal will become hot because of its inherent resistance. Increasing 
the current increases the resistance and consequently the tempera¬ 
ture. As can be readily understood, the disadvantage of direct heat¬ 
ing by resistance is that not only is the metal or substance heated, 
but likewise all the conductors that carry the current to it. For this 
reason copper, which lias a much lower specific resistance than iron, 



Figure 7. —Curve representing a complete wave or cycle of alternating current. 


is used for a conductor. If an electric current be passed through a 
copper and an iron wire, each of equal cross section, greater heat is 
developed in the iron wire, in the proportion of 0.1 to 0.018; hence if 
the wires are of equal lengths the total amount of heat developed in 
the iron wire will be much greater than that developed in the copper 
wire. 

INDUCTION HEATING. 

In order to define precisely what is meant by induction heating, 
it is necessary first to outline the principles upon which such heating 
is based. As is well known, in a direct electric current the flow 
is always in the same direction, whereas in an alternating cur¬ 
rent the direction of flow is constantly being reversed. The time 
required for a change of direction is called a period. In figure 7, 
which shows a complete wave or cycle, T represents the time neces¬ 
sary for the current to swing through a complete wave; that is, from 
0 (zero) to the positive maximum, back to zero, to the negative maxi¬ 
mum, and back to zero. If an alternating current be passed through 
a coil of wire and if a conductor be passed through the magnetic field 

a For the convenience of those not familiar with the same, some of the fundamental laws and terms of 
electrical engineering are given in the Glossary (pp. 186-189). 




























14 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


of the coil in such a way as to cut the lines of force of the field a cur¬ 
rent is induced in the conductor. A magnetic field is shown in figure 
8 in which n and s are the poles of a magnet and c is a wire conductor 
(shown in cross section) that is made to cut the lines of force passing 


between the poles. 

In what is known as a transformer the conductor is kept stationary, 
and the field is made to change or to move across the conductor. If 
a coil of wire be wound around a core of soft iron and a current 
passed through the wire, a magnetic field is produced as with a per¬ 
manent magnet. If the current be suddenly made and broken or if 
an alternating current be used, the magnetic flux will increase and 
decrease in first one direction and then the other. Now by winding 
a second coil of wire on the iron core a conductor is obtained. Every 
time the magnetic flux (lines of force of the field) increases or decreases 
in strength as it changes its direction a current will be set up or 
induced in the second coil or secondary winding and in a direction 

that tends to oppose the 

^__ —flow of current through 

the first coil or primary 
winding. 

The current induced 
in the secondary wind¬ 
ing will be inversely 
proportional to the num¬ 
ber of turns on the wind¬ 
ing and consequently 

(by Ohm’s law, y = I\) 





TL 





■ ct— x—cr 

■\ 

• \ 

1 \ 
1 1 
1 

1 

1 

1 

1 

» 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

• 

1 

1 

1 

1 

1 

1 

1 

1 

1 / 



' \ \ 

' \ \ 

' N \ 


/ / ' 
/ • 
✓ / 


Figure 8.—A magnetic field, in which a conductor has been 

placed. 


the voltage will be in direct proportion. The foregoing relation does 
not hold exactly true because the resistance and other properties of 
the transformer become factors in the application of this law. 

With a given voltage the larger the current to be carried the lower 
must be the resistance of the conductor. The resistance can be low¬ 
ered by using a conductor of larger size or one made of a material that 
is a better conductor of electricity. In electrical work copper is gen¬ 
erally used for conductors. 

From these statements it is evident that heat is generated when an 
electric current is induced in a conductor, and if the conductor has a 
high specific resistance, such as that of the bath of steel in an induc¬ 
tion furnace, the heat developed is in proportion to the square of the 
resistance and to the strength of the current induced. This method 
of heating may be termed heating by induction, and it is most used 
in electric-furnace practice in steel furnaces, such as those of Kjellin, 
Colby, and Rochling-Itodenhauser, which are known as induction 
furnaces. 

















DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 15 

CONSTRUCTION OF THE INDUCTION FURNACE. 

On analyzing the induction furnace its method of construction is 
found to be based on three essential features, as follows: (1) A pri¬ 
mary winding composed of a great many turns of wire or other con¬ 
ductors, (2) a core or circuit for the magnetic flux, and (3) a circular 
trough containing molten steel, which corresponds electrically to a 
secondary winding of one turn. 

As the secondary winding is of only one turn, an enormous current 
can be induced in it, and as the steel is not an exceptionally good con¬ 
ductor it becomes heated to a high temperature. For example, in 
such a furnace as the Kjellin steel furnace the. primary winding rep¬ 
resents the conductor, through which is passed a current of 90 
amperes at 3,000 volts. Around this winding is a circular trough 
which contains the metal. As the current passes through the primary 
winding, a magnetic flux, or flow of current, is induced in the metal 
in the trough, and the current is transformed from 90 amperes at 
3,000 volts to 30,000 amperes at 7 volts. By reason of the high 
amperage of the induced current and the resistance with which it 
meets in the metal in the trough, sufficient heat to melt the metal is 
generated. 

Although this type of furnace possesses certain advantages, it also 
possesses several disadvantages, chief among these being that it 
is inefficient in much the same sense as a poorly constructed trans¬ 
former is, owing to the fact that it is built on the principle of a trans¬ 
former. Moreover, when used for heating a metal such as steel, 
there is also induced in the bath of the induction furnace electro¬ 
mechanical forces, which are discussed in another chapter, that have 
a tendency to interfere with the working of the furnace. 

INDIRECT-RESISTANCE HEATING. 

In the indirect-resistance method of heating the heat is not pro¬ 
duced by using a metal as a resistor, but by passing the electric cur¬ 
rent through some substance that has a very low electric conductivity. 
An example of such a furnace is the Acheson carborundum furnace 
(fig. 3). In this furnace the charge to be heated is placed around the 
carbon core. An electric current is passed through the core, which 
thus becomes hot and in turn heats the charge. 

When materials such as crucible steel are heated in crucibles, 
an indirect method of heating is employed. The crucible furnaces 
are fired with either coal or gas and have lov T efficiency (see table, 
p. 4), owing to the amount of heat that is carried away with the 
flue gases. The Girod crucible furnace a (fig. 9) was devised to do 
the same kind of work as the ordinary crucible steel furnace. In the 


a Vom Baur, C. II., Electric furnaces in the iron and steel industry, 1913, p. 33. 





16 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Girod furnace shown in the figure the current is conducted through 
the bottom, which is made of materials having high electrical resist¬ 
ance, such as carbon and silica. In furnaces of this kind temperatures 

of 1,400° to 1,700° C. have been 
reached. In another Girod 
crucible resistance furnace a 
resistor of ferrosilicon is used, 
to which the current is led by 
four carbon blocks around the 
crucible. 

Still another type of indirect- 
heating furnace is the Hei- 
berger furnace (fig. 10). This 
furnace consists of a crucible 
which is placed in circuit by 
means of carbon contacts, so 
that the current passes vertically through the crucible walls. Hel- 
berger uses the ordinary carbon or graphite crucibles. 

ARC HEATING. 

Arc heating was employed by Moissan in his famous researches. 
In figure 11 is shown the Moissan type of furnace, which is described by 
Stansfield® as follows: 

It consists of two blocks of limestone and two carbon rods, to which electrical con¬ 
nections are made. A cavity is hollowed out in these blocks, and the material to be 
heated is placed in a crucible of carbon or magnesia. As even lime melts and volati¬ 
lizes at the temperature of this furnace, a lining of alternate layers of carbon and mag¬ 
nesia was arranged as shown in the figure, 
in order to withstand, as far as possible, 
the heat of the arc. 

In some of these experiments Moissan 
converted two or three hundred electrical 
horsepower into heat in a furnace of only 
a few inches internal dimensions. At the 
enormously high temperature of his fur¬ 
nace everything melts or turns to vapor. 

Carbon is the most refractory substance 
known, and even that turns to graphite and 
volatilizes; magnesia, another very refrac¬ 
tory substance, melts at the highest tem¬ 
perature of the furnace and vaporizes. 

Lime, quartz, and alumina melt and Fioure 10 ._ C ro S s section of Ilelberger furnace, 
boil in the furnace. Gold, copper, iron, 

and in fact all the metals, can also be melted and boiled in such an electrical 
furnace. 

An improved form of the Moissan furnace was described in Engineering &, March 
23, 1906, in which an electric current of 1,000 amperes at from 50 to 150 volts is em- 




Figure 9.—Cross section of Girod furnace. 


a Stansfield, A., The electric furnace, 1907, p. 19. 

b Anon., One-thousand ampere Moissan eleetric furnace: Engineering, vol. 81, 1906, p. 381. 





























































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


17 


ployed. In the case of direct current this would mean 70 to 200 horsepower, and, 
while this is not quite as much as Moissan sometimes used, it is more than is often 
available for scientific experimental work. In such a furnace it is easy to produce a 
temperature more than double that usually obtainable by the combustion of fuel, 
and it is, therefore, an invaluable apparatus in the hands of the metallurgist and „ 
the chemist. 

Arc heating by radiation finds its practical application in the 
Stassano furnace, shown in figure 5. 



FACTORS AFFECTING EFFICIENCY. 

As the various types of heating used in electric-furnace work have 
been outlined, and as the most important factors connected with the 
use of the electric current for this purpose have been presented, the 
bearing of these factors on the efficiency of the furnace will now be 
considered. 

INDUCTION CURRENTS. 

SELF-INDUCTION. 

As previously stated, the strength and direction of an alternating 
current are continual^ changing—twice during each period or 
cycle it increases from zero to a maximum and then decreases to zero 
again. Owing to this fact, a conductor carrying alternating currents 
is surrounded by an alternating magnetic field, which, as has been 
shown, induces currents (electromotive force) in all conductors within 










































18 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

the field. As the conductor carrying the alternating current necessa¬ 
rily lies in the magnetic field, a current is induced within the conduc¬ 
tor by its own field. This effect is known as self-induction, and the 
resulting current is known as the self-induced current. 

As such a current may cause considerable loss of power under 
certain conditions, it is well to understand these conditions and as 
far as possible avoid them in the construction of electric furnaces. 

An induced current is generated in every conductor that is parallel 
to the main current, hence care should be taken not to short-circuit 
the conductor carrying the induced current, since this may cause 
heavy losses of power. For example, in designing a furnace, an iron 
beam should not be placed in such a position as to cause the conductor 
to be short-circuited on itself. Likewise the cables and bus bars leading 
from the transformers to the furnace should be placed close together, 
for in this way there is no action on closed iron parts, or parts that 
lie parallel to one another, and thus the magnetic fields, as for exam¬ 
ple those made by two conductors of a single-phase current, are 
neutralized. These conditions are of importance only when heavy T 
currents are employed, but heavy currents are usually used in electric- 
furnace work. One must remember also that currents are induced 
in all metal parts that are near a conductor. 

EDDY CURRENTS. 

The currents that are induced in the metal parts of a furnace are 
called eddy currents. As the metallic parts are good conductors, 
through which the current may be short-circuited, these parts if im¬ 
properly placed may become decidedly hot and cause more or less 
trouble. This is especially true when the metal is magnetic, that 
is, a good conductor of the magnetic lines of force. For example, in 
furnaces in which the current is led to the electrodes through electrode 
holders, making these holders of cast iron or steel will cause consid¬ 
erable loss. For this reason the holders, which are generally water- 
cooled, are made of copper or brass, neither of which is magnetic. 

Another method of lessening eddy-current losses is to greatly 
subdivide the metallic parts in which eddy currents are likely to 
occur, as is done, for example, in transformers and in armatures of 
dynamos. 

HYSTERESIS. 

There is also another loss from what is known as hysteresis, the lag 
of demagnetization. This loss occurs in magnetic conductors having 
considerable cross section and is due to the constant magnetizing and 
demagnetizing influence of the alternating current. Therefore, in 
furnace construction, the electrical conductors should not be sur¬ 
rounded by parts that are good magnetic conductors. 


DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


19 


LAG. 

If an electric current be passed through a coil of wire, the current 
does not immediately reach its maximum value, hut does so only after 
a certain time has elapsed. In other words, the current lags behind 
the voltage, and this is known as the lag of the current. 

ELECTROMECHANICAL FORCES IN THE INDUCTION FURNACE. 

The nature and effect of the mechanical forces of electric origin in 
the bath of the induction furnace, although at present well under¬ 
stood, are still to many a source of apprehension in the design and 
operation of this type of electric furnace. These electromechanical 
forces, which often are of considerable magnitude, are of two kinds: 
(1) Attracting, due to the mutual attraction of current-carrying 
elements within the bath, similar to the attraction of two parallel con- 



Figure 12.—Cross section of the bath of an induction furnace, showing effect on surface of bath of 

the resultant of the different forces acting. 

ductors carrying current in the same direction; and (2) opposing, due 
to the repelling action between the bath and the primary winding, 
similar to the repelling action of two conductors carrying current in 
opposite directions. 

PINCH EFFECT. 

Attention was several years ago called to the first of these forces 
by E. F. Northrup and later by C. Ilering, who observed a contraction 
in the cross section of the bath. The contraction was frequently 
so pronounced that complete rupture resulted. This phenomenon 
has since been generally referred to as the pinch effect. ” 

In figure 12 the circle represents the cross section of a circular 
conductor. The tendency of the electromagnetic forces of the fiist 
class mentioned is to act radially and their manifestation is a me¬ 
chanical effect, the liquid particles constituting the conductor mov¬ 
ing bodily in the direction of the forces. If, by suitable means, the 
pressure in the bath be measured, it is found to be greatest at the 
center and least at the periphery. For the pressure at the center 

















20 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


of a bath having a circular cross section, the following formula has 

/ 2 

developed: P = > m which P is the pressure in dynes per square 

centimeter, I is the current in c. g. s. units (10 amperes), and S is 
the cross section of the bath in square centimeters. 

Although the formula holds precisely true only for conductors of 
circular cross section, no great error is involved in applying it to the 
practical working conditions of the induction furnace. 

In the bath of an annular crucible of ideally uniform cross section, 
this pressure would not produce the contraction known as the pinch 
effect, but in practice the cross section is never uniform, because of 
dissymmetry in the crucible, or of deflection of the plane of the cruci¬ 
ble from the horizontal, or of the presence in the bath of unmolten non¬ 
conducting material, such as floating pieces of ore or brick. When¬ 
ever the cross section of the bath is reduced by any cause the pressure 
is locally increased and the result is a lateral force causing a flow to 
adjacent areas of lower pressure. An increase in the current will 
augment this effect and if the current is further increased a limit is 
reached, when the liquid is 11 squirted” out from the spot of high 
pressure faster than it can return, and a break in the circuit results. 
If the bath is mobile, the circuit will continue to close and open until 
freezing occurs. 

The working limits imposed upon induction furnaces by the pinch 
effect have been studied and a formula developed, by means of which 
the critical current values can be calculated approximately. Expe¬ 
rience has shown that the pinch effect does not cause difficulty in the 
operation of large induction furnaces, such as are used in steel making, 
for in these the values of the currents used are far below the critical 
points. The pinch effect, however, has thus far made impracticable 
the melting in an annular crucible of metals of low specific gravity, 
such as aluminum. Metals of low specific resistance, such as copper, 
are likewise less amenable to working in induction furnaces of the 
annular type, because heat generation is a function of the specific 
resistance, and when the specific resistance is low greater current 
density is required, which may exceed the critical value for the 
furnace. 

From the standpoint of metallurgists the mechanical effects of the 
magnetic forces set up in the bath of the induction furnace are of 
value. The resulting circulation of metal in the crucible assists the 
heating by increasing convection and accelerates chemical action by 
bringing the reacting substances into more intimate mixture. Appre¬ 
ciation of these advantages has inspired efforts to design on the 
induction principle a furnace in which the danger of “pinching” will 
be eliminated but the desirable effect of increased circulation retained. 


DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 21 

Such a. furnace has been constructed and although still in the devel¬ 
opment stage promises speedily to find peculiar and important appli¬ 
cation in the melting of metals. 

CENTRIFUGAL EFFECT. 

Electromagnetic forces of the second class are set up between the 
bath and the primary winding. Their mechanical manifestation in 
the bath resembles in many respects the effect that would be produced 
by rotating the annular bath on its axis, and for this reason the name 
“centrifugal effect’’ has been given it. 

This repelling force between the primary winding and the bath of 
a single-ring induction furnace is analogous to the repelling forces 
between the windings of a core transformer, and the theory and cal¬ 
culations for the later forces may be applied to the induction furnace, 
as the induction furnace is in fact equivalent to a transformer with a 
short-circuited secondary. 

In addition to the centrifugal force mentioned a second force 
acting upon the bath is gravity. In figure 12, representing the cross 
section of the bath of an induction furnace, if oa be considered to rep¬ 
resent the centrifugal force of electromagnetic origin and ob gravity, 
the surface of the bath must be perpendicular to the resultant force oc. 
As the tendency of the pinch effect is to give the bath a circular cross 
section, the result of all the forces acting on the bath is to give its 
cross section the form shown on the left. In large furnaces operating 
at full load the surface of the bath is inclined about 30° to the hori- 

4 

zontal. 

There is no danger of the circuit breaking as a result of the cen¬ 
trifugal force on the liquid bath. When a solid starting ring breaks, 
however, the break is invariably due to the centrifugal force, which 
has exceeded the tensile strength of the ring. 

The centrifugal effect, like the pinch effect, tends to eliminate 
inclosed gases by compression of the bath against the outer wall, and 
also causes circulation at right angles to the direction of the bath. 
In some large furnaces, such as the Frick and the Iliorth, sections of 
the primary winding are placed above and below the bath, thereby 
moderating the circulation and removing the danger of the starting 
ring being broken. 

POWER FACTOR. 

MEASUREMENT OF POWER FACTOR. 

The power supplied to a furnace in watts is for a direct current the 
product of the number of amperes and the number of volts, whereas for 
an alternating current it is the product of the number of amperes and 
the number of volts, multiplied by a factor known as the power factor, 


22 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

which varies with the construction of the furnace, as explained later. 
In this connection, it may be stated that alternating current is used 
almost entirely in furnace work, for two reasons. First, almost all 
large electric-power installations generate alternating current, and 
hence at most places only alternating current is available for furnaces, 
unless the current be transformed by means of a motor generator set 
into direct current. Moreover, a direct current is not necessary, and 
in fact is undesirable in furnace work, because it exercises an electro¬ 
lytic action on the metals produced. 

The power (watts) delivered to the furnace may be kept constant 
by keeping the voltage low and the amperage correspondingly high, 
or by keeping the voltage high and the amperage correspondingly low. 
If, for example, a furnace be built for 50 kw. (50,000 watts) at 50 volts, 
if the power factor were neglected, the ammeter would show 1,000 
amperes; in other words, the number of watts divided by the num¬ 
ber of volts gives the number of amperes. For currents of large 
amperage large conductors are required, thus increasing the cost of 
cables, transformers, electrodes, and other equipment. The use of 
a high voltage, although economical, is generally impractical, because 
most furnaces have a low electrical resistance. For example, in the 
Swedish and California types of electric iron-reduction furnaces the 
resistance is in the neighborhood of 0.01 ohm, and the voltage used 
varies from 40 to 80 volts with a three-phase furnace. With an 
average load of 500 kw. on each phase, the corresponding number of 
amperes per phase would be 10,000. Thus it is seen that having to 
handle electric currents of high amperage is one of the disadvantages 
of electric-furnace work of this nature. 

USE OF ohm’s LAW. 

As previously stated, the power used in a furnace, measured in 
watts, is for direct current the product of the number of amperes and 
the number of volts, whereas for alternating current it is the product 
of the number of amperes and the number of volts, multiplied by a 
factor known as the power factor. If the relations between the alter¬ 
nating and the direct current be compared, it will be found that for the 
direct current a definite voltage is required to force a current, /, 
through a resistance, R, and, according to Ohm’s law: 

E (electrical pressure )—I X R 

In order to force an equal alternating current, /, through a resist¬ 
ance (the resistor, the charge, or whatever is used in a particular case), 
the fact already explained must be taken into account—that with the 
alternating current an electromotive force due to self-induction is 
generated, which is always in the opposite direction to the impressed 


DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


23 


electromotive force. Therefore instead of the equation being 
E= IxR, it must be written as E r =IxR, and as an additional pres¬ 
sure (voltage) is needed to overcome the electromotive force of self- 
induction, the total voltage necessary for an alternating current is 
E=E r +E 1 . 

In other words, the voltage of an alternating-current voltage has 
two different pressure waves, and instead of the power P on the fur¬ 
nace being expressed by the equation P=ExI, for alternating cur¬ 
rent the equation is P = El cos </>, where </> is the angle of lag or lead 
of current, because, as has been pointed out, the effect of capacity 
on the circuit is to cause the electromotive force to lag behind the 
current. Therefore, if the current either lags or leads, the readings 
of the instruments used for measuring the electric current at the fur¬ 
nace (the voltmeter and ammeter) are not true simultaneous values, 
and in order to get the true values the product of the number of volts 
and amperes shown on the instruments must be multiplied by a factor 
obtained in the manner above stated. 

Hence, in an alternating-current circuit the product Ex I is called 
the apparent power, and can be measured in volt-amperes or kilovolt¬ 
amperes, a kilovolt-ampere being equal to 1,000 volt-amperes. The 
product El X cos <£ indicates the real or effective power and is meas¬ 
ured in watts or kilowatts. Inasmuch as the determination of the 
cross section of an electrical conductor depends on the strength of 
the current the conductor is to carry, and the current strength de¬ 
creases with an increasing power factor, provided the voltage and 
power remain unchanged, it is of course desirable to obtain the highest 
power factor. 

As the ammeter and voltmeter on an alternating circuit do not in 
any way indicate what the power factor is, a special meter is used 
called the wattmeter, which indicates the watts or kilowatts directly. 
One kilowatt equals 1,000 watts. 

Because of the facts stated, it is evident that in designing a furnace 
a high-power factor should be sought. 

POWER CIRCUITS. 

As previously stated, most large power circuits are three phase, 
which means that three lines are needed to conduct the current from 
the source of supply to the point where it is used, whereas with 
single-phase current only two lines are necessary. 

In using a single-phase current the connecting of the electrodes to 
the source of supply is a simple matter, as may be seen by referring 
to figures 1, 2, 3, and others. If, on the other hand, three-phase 
current be used, three different types of connections may be used, 
as shown in figure 13. 

44713°—Bull. 77—16-3 



24 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


REGULATION OF THE ELECTRIC CURRENT. 

The current in an electric furnace may be regulated in one of two 
ways, as outlined below: 

1. Inasmuch as the electrical resistance in a furnace changes with 
the height at which the electrode is kept above the charge or bath, 
the electrode may be made movable and then raised or lowered as 
may be necessary. 


v 


w/ 



jW'AV 


AVWV- 


m 


VV\? 

yWvVj 


rtf 


|VWW 


5 


I 




\vJ~ 

jVvVA- 


3 


I 


w 

jWW| 



o 

\ 



tf 


Ifirt/ 






Figure 13.—Different types of electric furnace connections. 

2. The electrode may be kept stationary and the voltage varied 
by means of variable voltage transformers. 

The first method is employed in operating steel furnaces of the 
Heroult, Girod, and Electro-Metals type. The raising and lowering 
of the electrodes may be done by hand or by means of electric motors 
controlled by instruments regulated by the voltage of the furnace in 
such a manner as to keep the load constant. 

The second method is used on the Swedish and California types of 
furnaces. 





















































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 25 


Van Norden 0 describes the eJectric control of the electric iron 
smelting furnaces of the Noble Electric Steel Co. at Heroult, Cal., 
as follows: 

Electric control is through a switchboard, there being a panel for each furnace. As 
the current and power factor in each phase must be under observation at all times 
during operation, separate meters are installed in each phase. The requirements foi 
one panel are three ammeters, three voltmeters, three wattmeters, three power factoi 
meters, and three recording wattmeters. These are mounted across the panel in rowk. 
of three each. Under the first four sets named are three handwheels to control th<i 
voltage variation, and under these, three switches which control the entire load, an<i 
still under these are the recording wattmeters. 

For operating the voltage control and the main circuit breakers there is a 7^-kilowaW 
motor-generator set, comprising a 125-volt direct-current generator, directly connected 
to a 10-horsepower induction motor. This set has a small panel-board mounting, a 
circuit breaker, ammeter, voltmeter, and two single-pole knife switches. * * * 
In the event that line voltage should fall, or for any other cause, the direct current 
supply should become deranged, there is a * * * storage-battery set, having a 
capacity of 7£ kilowatts which may be instantly switched in, and thus prevent the 
furnace from cutting out in the case of low voltage. 

ELECTROLYSIS. 

Although the electrolytic or decomposing effect of the electric cur¬ 
rent finds more extended application in the electrochemical indus¬ 
tries than it does in the production of metals from their ores, it is 
nevertheless more or less used for the latter purpose, especially in 
the production of aluminum, and for that reason is briefly discussed 
at this point. 

ELECTROLYSIS OF WATER. 

The electrolysis of water is a familiar example of the decomposing 
effect of the direct electric current. By the use of such a current 
water can be resolved into its component elements, hydrogen and 
oxygen. In order to do this the terminals of a direct electric current 
are inserted into a dish or glass containing the water. The positive 
terminal is known as the anode, and the negative as the cathode. 
When the current is turned on, it passes through the water from the 
positive to the negative terminal (from the anode to the cathode), 
and electrolyzes or decomposes the water. The hydrogen is liberated 
at the cathode, or negative terminal, which may be designated the 
negative electrode, and the oxygen is liberated at the anode or 
positive electrode. 


ELECTROLYSIS OF COPPER SULPHATE. 

Similarly, if a direct current be passed through a solution of copper 
sulphate, which, in such case, is termed the electrolyte, copper will 
be deposited at the cathode and sulphuric acid gas will be given off 
at the anode. In refining cast copper, the anode is made of the 


a Van Norden, R. W., Jour. Elect. Power and Gas, vol. 29,1913, p. 1. 



26 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


impure metal, and a solution of copper sulphate is used as the electro¬ 
lyte. Under the action of the electric current, the copper anode dis¬ 
solves, and pure copper is redeposited at the cathode. Any substances 
other than copper in the anode, are, if the current is properly regu¬ 
lated, liberated and collect on the bottom of the tank containing the 
electrolyte. 

PREREQUISITES OF AN ELECTROLYTE. 

In electrolyzing a solution of copper sulphate, the water, which is 
a more stable combination than copper sulphate, is not broken up, as 
the current acts on the least stable compound. On the other hand a 
solution of aluminum sulphate is more stable than water, and hence 
an electric current would decompose the water and not the aluminum 
sulphate. Such being the case, the following prerequisites must be 
observed in preparing an electrolyte, namely: For the substance to 
be electrolyzed a solvent that is more stable than the salt, or the pure 
salt in a state of fusion, must be employed. Aqueous solutions must 
be avoided when the water can react with the metal produced. For 
example, an aqueous solution can not be used in the production of 
metallic sodium, because water reacts with sodium, forming caustic 
soda and hydrogen. 

ESSENTIAL DETAILS OF ELECTROLYSIS. 

In electrolytic work, the quantity of metal produced depends 
chiefly on the quantity and voltage (electrical pressure) of the current 
that is passed through the electrolyte, thus bringing about a definite 
amount of decomposition which is always the same for the same 
solution. The quantity of metal that will be liberated by electrolysis 
per unit of time by a given current may be calculated in the following 
manner: If a current of 1 ampere be passed through acidulated 
water for a period of one secohd, 0.0104 milligram of hydrogen will 
be liberated. Therefore, the quantity of metal obtainable by passing 
a like current through a copper sulphate solution may be determined 

from the equation ® ^ ^ = x, in which C represents the constant 

0.0104, W the atomic weight of the metal, and V the valency of the 
metal in the particular solution. However, the quantity of metal 
shown by this calculation is not always obtained, owing to the 
secondary reactions that take place, such as the liberation of hydrogen 
instead of the metal, the redissolving of metal in the electrolyte, and 
the leakage of the current. For this reason, what is termed current 
efficiency, by which is meant that proportion of the current that is 
effective in liberating the metal, has to be taken into consideration. 

In order to pass a stated quantity of electrical energy through a 
given solution in a stated time, the electrical current must be kept at 
a definite voltage, or pressure, for that particular solution. Below 
this pressure, or voltage, electrolysis will not take place. 



DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 27 

Inasmuch as the current in passing through the electrolyte meets 
with resistance, heat is generated, the quantity of which is proportional 
to the square of the current and to the resistance of the electrolytic 
cell. As this generation of heat represents the expenditure of elec¬ 
trical eneigy, the higher the temperature, the less efficient is the 
decomposing effect of the current. However, in the electrolysis of 
fused salts or compounds, the heat generated through the resistance 
of the electrolyte to the passage of the current serves to keep the 
electrolyte fused and so is of use instead of being wasted. 

The nature and the composition of the anode are of great impor¬ 
tance in electrolytic work. If possible the anode should meet the 
following seemingly contradictory requirements: The anode material 
should be insoluble in whatever is liberated in contact with it as the 
result of the electrolytic action of the current, but if the material is 
soluble, it should be inexpensive, for it will be dissolved in proportion 
as the metal is deposited. In the manufacture of aluminum, the 
carbon electrodes (the anodes) are consumed by the oxygen liber¬ 
ated by the decomposition of the alumina of the electrolyte into 
aluminum and oxygen, and the weight of electrodes consumed about 
equals the weight of aluminum produced. On the other hand, as re¬ 
gards the amount of energy needed to break up a given weight of 
compound into its elements, more voltage is required for an anode 
that does not dissolve than for one that does. 

In electric-furnace work, electrolysis is involved in reducing metals 
from ores when the metal is present in the form of a salt or a mixture 
of salts winch must be fused and the metal deposited from the fused 
mixture by a direct electric current. 

MECHANICAL CONSTRUCTION OF FURNACES. 

The electrical side of the subject has been briefly discussed in the 
foregoing pages. The factors that must be taken into consideration 
in the actual construction of an electric furnace will now be noted. 

FACTORS AFFECTING OUTPUT. 

Naturally, in the construction of a furnace, the first matter to be 
taken into consideration is output. Inasmuch as a small furnace, 
using a comparatively large amount of power, may produce as much 
as a larger furnace using a comparatively small amount of pow 7 er, 
the nature of the process must be considered in deciding what size 
of furnace will be employed. Then, too, one must remember that 
large electric furnaces, large as compared with modem copper and 
iron blast furnaces, have not been successfully operated as yet, and 
hence if the desired production is, say, 100 tons or more of metal a 
day, the size of the unit to be employed will first have to be deter¬ 
mined. As regards this point, the facts that should be borne in mind 
are as follows: (a) The relative loss of heat through the walls is less 
for a large than for a small furnace, and therefore each unit should 


28 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


be as large as may be feasible; but ( b ) in order to reduce the total 
heat loss the furnace should be as small as possible for the stated 
output. 

In other words, for a given output a smaller furnace is more efficient 
than a larger furnace, but, as before stated, the nature of the process 
must be taken into consideration in determining relative economy. 
As a comparatively large amount of energy is required to keep the 
temperature of the furnace uniform, it is of course better to employ 
continuous processes wherever feasible, or to leave as little time as 
possible between charges if an intermittent process be used. 


CALCULATION OF ENERGY REQUIRED. 

When the output of the furnace has been determined, the amount 
of energy that will be required to give this output has to be calcu¬ 
lated. In this calculation the following factors have to be taken into 
consideration: (a) The heat available from such chemical reactions 
during the process as give up heat, that is, as are exothermic. Illus¬ 
trations of such reactions are the burning of carbon to carbon monox¬ 
ide, or of carbon monoxide to carbon dioxide, or the formation of 
a silicate. The other factor is ( b ) the heat that is absorbed during 
the process. The absorbed heat includes that required to raise the 
raw material to a smelting temperature, or to a temperature at which 
the reactions necessary to the process take place, and also the energy 
that is absorbed in such reactions, as for example, the reduction of 
iron oxide to iron, of silica to silicon, or of calcium from calcium 
oxide. Almost all of these changes involve the specific heat, gen¬ 
erally the latent heat of liquefaction, and sometimes, too, that of 
vaporization. Also, allowance must be made for loss of heat by 
conduction through the furnace walls and through the electrodes. 
These losses are discussed in subsequent pages. 

As a result of these calculations a heat balance sheet of the process 
may be constructed. The following example a will serve to illustrate 
this point. Let it be assumed that an iron ore is to be smelted and 
that the calculations for determining the amount of heat available 
and necessary show that for each ton of metal to be produced 
1,053,532 calories must be supplied electrically and that the desired 
output is 1 ton of metal per hour, then each ton will require 
1,053,532-^3,600 = 292 calories per second. The total horsepower 

required to furnish this heat, 29 " - X m - = ^654 horsepower. 

Which means that theoretically there would have to be supplied 
to the furnace a constant current of 1,654 horsepower in order to 
produce 1 ton of pig iron per hour. 


a For further information on the subject of calculations of this kind see Richards, J. W., Metallurgical 
calculations, 1907, pt. 2, p. 403; and Yngstroin, Lars, The electric production of iron from iron ore: Engineer 
(London), Feb. 26,1900, p. 206. 




DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


29 


CURRENT AND VOLTAGE NECESSARY. 

After the amount of current necessary to carry on the process has 
been ascertained, the voltage at which the current is to be supplied 
may be determined. The choice of voltage is governed largely by the 
construction of the furnace. Theoretically it is best to have the 
voltage as high as possible, but practical considerations generally 
prohibit the use of a high voltage, and hence a comparatively low 
voltage is used in electric-furnace work. For example, the voltage 
used for an iron-reduction furnace ranges from 40 to 80 volts, 50 
volts perhaps being the average. In the case of the Heroult steel 
furnace 90 volts is used for the three-phase furnace at South Chicago, 
whereas for a Heroult single-phase furnace a voltage of 100 to 110 
volts is ordinarily used. In an induction furnace the primary voltage 
may be as high as 3,000, whereas in the Moissan arc furnace it is 
about 110. As a rule, in arc furnaces the arc should be as long as 
other considerations permit. 

PROPER SIZE OF INTERIOR OF FURNACE. 

Of course waste space in the interior of a furnace greatfy diminishes 
efficiency. On the other hand, it is sometimes necessary to allow 
for what may seemingly be waste. For example, in the Swedish 
electric iron-reduction furnace the roof of the crucible is so con¬ 
structed as to allow a gas space between the surface of the charge and 
the roof. In this way the roof, at the point where the electrodes enter 
it, is somewhat protected from the heat developed in the charge. Or 
it may be found best to allow part of the material forming the charge 
to chill along the walls of the furnace in order to protect the walls. 
In such instances, however, the material must be considered as a part 
of the wall of the furnace and not an available part of the interior of 
the furnace. As a rule the interior of the crucible of the furnace 
should be made as small as practicable. 

The interior dimensions of some furnaces in actual practice are 
given belov: 

Dimensions of three f urnaces. 


Type of 
furnace. 

Location. 

Prod¬ 

uct. 

Ca¬ 

pac¬ 

ity. 

Power. 

Internal dimensions. 

Thickness of 
lining. 

Diam¬ 
eter of 
elec¬ 
trodes. 

a 

b£ 

d 

O) 

> 
k—1 

A 

rs 

•rH 

£ 

A 

a 

a> 

ft 

O'. 

'O 

fl 

ft 

a* 

2 

m 

o 

o 

Pi 

Heroult. 

Do.. 

Girod... 

B r a intree, 
England. 
South Chi¬ 
cago, Ill. 

U g i n e , 
France. 

j-Steel.. 
...do.. 

j..do.. 

Tons. 

2.5 

15 

2.5-3 

Kilowatts. 

300 

1,200-1,500 

300 

Ft. in. 
fa 4 2 
\ b5 2 
(<0 

1 a 3 
\ b 6 

Ft. in. 

1 8 

2 7 
( c ) 

3 

6 

In. 

} 31 
d 36 

} 31 

In. 

14 

In. 

12 

18 

In. 

12 

12 

In. 

14 

14 







a Bottom. b Top. c Circular; diameter, 120 inches. d Approximate. 































30 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


PROPER SHAPE OF CRUCIBLE. 

The next item to be taken into consideration after the cubic con¬ 
tents of the crucible has been determined is the shape of the crucible. 
Theoretically, the spherical form is best so far as heat losses and 
general efficiency are concerned, but here, as in the determination 
of all points that have to be considered in the construction of a 
furnace, the special requirements to be met rather than the theoretical 
considerations will have the most weight. 

TYPES OF FURNACE LININGS. 

The kind of refractories that will be used in the lining of the furnace 
will depend on the nature of the product—that is, whether it is to be 
a solid or a liquid, and whether it will be acid, basic, or neutral in 
its chemical action. 

ACID REFRACTORIES. 

Silica .— Silica sand, either as such or made into brick, is most 
commonly used when a siliceous refractory material is desired. A 
typical analysis of a silica sand is as follows: 

Typical analysis of silica sand. 

Per cent. 


Water. 0. 24 

Silica. 97.25 

Alumina and iron oxide.16 

Lime.08 

Alkalies.36 

Magnesia.39 

Lossym ignition.36 


When the sand is made into bricks a small percentage of lime or 
some other similar substance is used as a binding material. By 
reason of the binder the melting point of the bricks is lower than that 
of the pure sand, and bricks made of pure fused quartz would be more 
refractory. There is a possibility that such bricks may soon be 
available for use in furnace linings. A good silica brick should 
not contain less than 95 per cent of silica. 

Dinas brick .—The name Dinas was applied originally to a brick 
made in Wales, from a pure sandstone that contained as much as 
98.3 per cent and not less than 96 per cent silica. A Dinas brick 
that contains 98 per cent silica contains about 0.72 per cent alumina 
(A1 2 0 3 ) and 0.10 to 0.20 per cent each of iron oxide (Fe 2 0 3 ), lime 
(CaO), and alkalies. 

Although Dinas bricks are capable of withstanding high tempera¬ 
tures, they have a coarse texture, are rather friable and brittle, and 
do not withstand abrasion. Two grades of these bricks are used in the 









DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 31 

United States, one being imported and the other made in domestic 
plants. An analysis a of an American brick is as follows: 

Analysis of an American Dinas brick. 

Per cent. 


Si °2. 94.07 

Fe 2 0 3 and A1 2 0 3 . 3 . 66 

Ca0 . 1.39 

MgO. . 


The Dinas bricks differ from ordinary silica bricks in the binder 
used. In many silica bricks the binding material is clay, whereas 
in the Dinas bricks, as before mentioned, the binding material is a 
lime silicate. 

Ganister .—The term “ganister” is used loosely. According to Ful¬ 
ton 6 it means a siliceous material of about the following composition: 
Quartz, 83 per cent; clay, 13 per cent; and impurities and moisture, 
4 per cent. Any siliceous material containing silica and clay in the 
above proportions may be used as ganister, provided it does not 
contain fluxing ingredients enough to lower materially the refrac¬ 
toriness of the product. Ganister can be made by mixing a highly 
siliceous material with enough clay to act as a binding material. It 
is not used as bricks, but as loose material, which is tamped into 
place as in furnace bottoms. 

Fire day .—Fire clay is sometimes classed as an acid refractory and 
sometimes as a neutral one, owing to the fact that in different clays 
the proportions of siliceous and aluminous contents, which together 
should constitute 92 to 98 per cent of the clay, differ widely. The 
refractoriness of a clay depends upon the proportion of those constit¬ 
uents which tend to lower the melting point of the clay. For the 
most part these constituents are ferric oxide, titanium oxide, lime, 
magnesia, and oxides of sodium and potassium. Of these constitu¬ 
ents, ferric oxide probably lowers the refractoriness of the clay more 
than any other, especially if the clay also contains carbonaceous 
matter. Owing to the presence of the mineral, kaolinite fire clays are 
plastic when mixed with a comparatively small proportion of water, 
and for this reason are easily molded into bricks of any required 
shape. In practice it has been found that the texture of a brick 
governs to a certain degree its refractoriness. For instance, a brick 
made of a fine-grained clay is not as refractory as one made from a 
clay in which there is a large proportion of coarse particles, even if 
the two clays have the same chemical composition. The refractori¬ 
ness of a fire brick is much increased by the coarseness of texture;' 
that is, If a fire brick be composed of a ground mass of fine grains in 
which are embedded comparatively coarse grains, the greater the per- 


a Fulton, C. H., Principles of metallurgy, 1910, p. 334. 


b Fulton, C. H., op. cit., p. 335. 








32 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

centage of coarse grains the more refractory will be the brick. Ful¬ 
ton ° has shown that the principle involved is the same as that gov¬ 
erning the formation temperature of slags. 

BASIC MATERIALS. 

Lime. —One of the most abundant basic refractory materials, and 
theoretically one of the best, is lime (CaO), which has a melting point 
of about 1,900° C. Practically, however, pure lime is of no use as 
furnace lining because of the rapidity with which it slakes when 
exposed to air. It lias been found, 6 however, that if the lime be 
fused, it will resist moist air for several days, whereas ordinarily it 
will do so for only a few hours. 

Magnesia .—Probably the most important of the basic refractory 
materials is magnesia (MgO), which, in electric furnace work, is used 
mostly in the form of brick. The bricks are made by mixing 90 per 
cent of thoroughly burned magnesite with 10 per cent of incompletely 
burned material, which is added for the purpose of causing the bricks 
to set. The mixture is then molded into shapes and burned. 

The bricks are dense and hard, and can be heated up to 1,800° or 
1,900° C. The objections to the use of magnesia bricks are as follows: 

1. They are good conductors of heat, and when hot become fairly 
good conductors of electricity. 

2. They expand somewhat on heating and spall or flake off when 
subjected to sudden changes of temperature. 

3. They are liable to go to pieces if subjected to a heavy load when 
hot. 

4. They are liable to shrink and crack when heated to high fem- 
peratures. 

Electrically calcined magnesite .—If the magnesite be calcined in an 
electric furnace, where it is subjected to a much higher temperature 
than is the ordinary calcined magnesite, it is less liable to shrink and 
crack, and does not absorb carbon dioxide gas as readily as does 
ordinary calcined magnesite. Fitzgerald c states that several tons 
of magnesia have been electrically calcined and tested in a great 
variety of furnaces, and in every case excellent results have been 
obtained. He also states that a resistance furnace has been devel¬ 
oped that will calcine the magnesite to the desired degree. 

Bauxite .—Bauxite is used for making both basic and neutral refrac¬ 
tory linings, the nature of the chemical action depending largely 
upon the composition of the bauxite used. As compared with mag¬ 
nesia, bauxite, which is extensively mined as an ore of aluminum, is 
cheaper. It can be made into a very hard and tough brick, the tensile 


a Fulton, C. H., Principles of metallurgy, 1910, p. 272. 

b Fitzgerald, F. A. J., Refractories: Met. and Chem. Eng., vol. 10,1912, p. 129. 
c Fitzgerald, F. A. J., Loc. cit. 




DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 33 

strength of woich may be as much as 10 ; 000 pounds per square inch. 
When used for making brick, bauxite has to be selected with care, 
as it must contain enougn silica and iron oxide to make a firm brick 
through the combination and incipient fusion of the two oxides. On 
the otuer hand, it must not contain too much silica, as that lowers its 
refractoriness. If the brick is to be used as a basic refractory material, 
the silica content should not exceed 12 per cent. 0 The composition 
of a bauxite suitable for brickmaking is approximately as follows : b 

Approximate analysis of bauxite for making brick. 

Per cent. 


Silica (Si0 2 ). 4 to 7 

Iron peroxide (Fe 2 0 3 ). 3 to 5 

Alumina (ALO,). 00 

water(H,0)!... 30 


Although bauxite is very refractory, it must be almost completely 
calcined, a difficult attainment, before it can be used for furnace 
lining or else it will shrink excessively at furnace temperatures. 
Calcination causes it to lose its combined water and thus destroys 
its plasticity. Because of these disadvantages it is seldom used in 
electric furnaces. At Braintree, England, the Lakes & Elliott Foun¬ 
dry Co. have used bauxite bricks in the construction of the roof of 
their Heroult steel furnace. The roof lasts from 14 to 28 heats. 
The short life of the roof, as compared to the life of the roof of other 
furnaces, is doubtless due to the fact that the construction of the 
furnace was such as to prevent the usual amount of radiation. 

NEUTRAL LININGS. 

Carbon. —Carbon is neutral and is one of the most highly refrac¬ 
tory substances known. It is generally used in the form of lamp black 
or retort carbon. 

Although carbon is capable of withstanding the action of slags, 
it has the drawback of being readily attacked by metals which have 
a strong affinity for it. For this reason carbon in the form of brick, 
or rammed with tar, has never come into practical use in open- 
hearth furnace bottoms, but the bottoms of furnaces used for mak¬ 
ing ferro-alloys, such as ferrochrome and calcium carbide, are nearly 
all made of carbon. Moreover, these bottoms are as durable as any 
other part of the furnace, in fact more so. At the works of the 
Keller-Leleux Co., Li vet, France, the furnaces, when once charged 
and started, are run continuously for an average period of a couple 
of years. The company states that the period may be made as long 
as four years. 6 Also, when, in 1912, one of the authors of this bul- 

a Fulton, C. H., Principles of metallurgy, 1910, p. 340. 
b (Editorial), Met. and Chem. Eng., vol. 8, 1910, p. 107. 

c Copeman, S. M., Bennett, S. R., and Hahe, H. W., Manufacture and transport of ferrosilicon: Met. 
and Chem. Eng., vol. 8, March, 1910, p. 135. 







34 


THE ELECTEIC FUENACE IFT METALLUEGICAL WOEK. 


letin visited the plant of the Meraker Electric Smelting Co., Kop- 
peraaen, Norway, he was informed that one of its furnaces, which 
have carbon bottoms and are used in the production of ferrochrome 
and calcium carbide, had been running continuously for 22 months 
and the other for 6 months. That the carbon bottoms in these 
furnaces are not destroyed is probably because enough carbon is 
added to the charges to satisfy the alloys produced and because the 
bottoms are not exposed to oxidation. 

The bottoms are made of lampblack or retort carbon, which is 
mixed with tar, heated, and then rammed into place. 

Chromite. —Chromite, usually termed chrome iron ore, is a sesqui- 
oxide of chromium. A typical analysis of chromite is as follows: 


Typical analysis of chromite. 

Sesquioxi.de of chromium (Cr 2 0 3 ). 

Alumina (A1 2 0 3 ). 

Iron peroxide (Fe 2 0 3 ). 

Silica (Si0 2 ). 

Magnesia (MgO). 


Per cent. 
38 to 40 

24.5 

17.5 
3. 25 

15-0 


Although chromite is extremely infusible, this property has the 
disadvantage of making its thorough sintering difficult. For this 
reason, chromite, although not affected by comparatively high tem¬ 
peratures, will not withstand mechanical erosion, and hence is not 
suited to furnace bottoms. It is well suited to the construction of 
furnace walls above the slag line, where they are not subjected to 
mechanical erosion of any sort. 

Alundum .—Alundum is made by purifying and fusing bauxite in 
an electric furnace. Two forms, a white and a brown, the former 
being the purer, are on the market. The melting point of white 
alundum is between 2,050° and 2,100° C. and that of the brown 
product is not more than 50° lower.® 

Alundum has been formed into bricks which were used for making 
the roof of an electric furnace. In this same furnace a roof built of 
silica brick was destroyed in 5 or 6 hours, wffiereas the alundum roof, 
at similar temperatures, lasted 40 or 50 hours. However, as pointed 
out by Fitzgerald, 5 although alundum bricks are capable of with¬ 
standing high temperatures when used in the construction of the 
roof of an electric steel furnace, they are not entirely suited for such 
construction for the following reasons: 

1. The lime vapors that rise from the intensely heated basic slag 
in the furnace react with the alundum brick and in time destroy 
the roof. 


a Fitzgerald, F. A. J., Refractories: Met. and Chem. Eng., vol. 10, March, 1912, p. 129. 
b Fitzgerald, F. A. J., Idem. \ 









DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 35 

2. Although alunclum bricks outlast silica bricks, yet because of 
their extra cost their use in electric-furnace construction is not 
warranted. 

Carborundum .—When sand, sawdust, and coal are heated together 
in an electric furnace at a high temperature, a carbide of silicon is 
formed which is known as carborundum. This carborundum may 
be crushed and made into brick by mixing the crushed product with 
a suitable binder, such as tar, glue, or sodium silicate. The fusing 
point of carborundum itself is about 2,200° C. Three samples of 
carborundum brick were recently submitted to the Bureau of Stand¬ 
ards for examination, and the melting point of all three proved to 
be about 1,720° C. The failure of these bricks was due to the destruc¬ 
tion of the binder, not to the fusion of the material as a whole. 
After the binder is destroyed, the remaining material has too little 
strength to last as a brick, often crumbling from its own weight. 
The binding material is largely vaporized, perhaps after a chemical 
reaction with the carborundum, as is shown by a considerable loss 
in weight and by the remaining material containing practically noth¬ 
ing but carborundum. All three samples behaved in practically the 
same way under test. When they were heated in a vacuum, loss of 
the binding material became noticeable at about 1,725° C. and 
became rapid at 1,750° C. When the samples were heated at atmos¬ 
pheric pressure, loss occurred at those temperatures, but it did not 
become rapid until a higher temperature was reached. At 1,860° C. 
considerable changes occurred in half an hour. 

Crystolon .—Crystolon is a trade name given to a crystalline form 
of carborundum made by the Norton Co. Being crystalline, it is 
made at a higher temperature than the amorphous form and is more 
refractory. The Norton Co. and the Fitzgerald & Bennie laboratories 
have done a great deal of experimenting with crystolon as a refractory 
material. Fitzgerald a describes the results of the experiments as 
follows: 

Under ordinary conditions crystolon is infusible, but when heated to a sufficiently 
high temperature in a reducing or neutral atmosphere it is decomposed, silicon 
vaporizing and the carbon remaining behind as graphite. If heated to a sufficiently 
high temperature in a strongly oxidizing atmosphere, slow oxidation occurs, the 
carbon burning to carbon monoxide and the silicon forming silica. The latter appears 
to form a protective coating which prevents further oxidation, or at least prevents it 
from proceeding rapidly. 

Fitzgerald 5 has patented a method for making crystolon into any 
desired form without the use of a binding agent. He mixes finely 
pulverized silicon carbide with some temporary binder, such as a 
solution of glue or dextrine, molds the mixture into the desired form, 
and then heats it in an electric furnace to the temperature at which 


a Fitzgerald, F. A. J., Refractories: Met. and Chem. Eng., vol. 10,1912, p. 129. 
b Fitzgerald, F. A. J., U. S. patents 650,234 and 650,235. 






36 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


silicon carbide is formed. This causes a crystallization or recrystal¬ 
lization of the silicon carbide, and a strong, very refractory article 
is obtained. 

As one of the greatest drawbacks to the use of the electric furnace 
in metallurgy has been the difficulty of maintaining the roof of the 
crucible, the possibility of using crystolon bricks in roofs is most 
important, and it is to be hoped that the material will prove satis¬ 
factory for this purpose. 

SUITABLE REFRACTORIES. 

The selection of a suitable refractory for electric furnaces is often 
difficult. After decision has been reached as to whether an acid, 
basic, or neutral refractory is desired, the next step is to determine 
which may be the best refractory under the conditions to be met. 

Owing to defects in the process of manufacture, the melting point 
of a brick is not always a measure of its refractoriness. For example, 
the use of fire-clay brick as a refractory may be contemplated, and two 
samples may be submitted for examination. One is found to have 
a lower melting point than the other, and so it may be said to be 
less refractory, but in service the one with the lower fusion point 
may be found to last three to five times as long as the one with the 
higher fusion point. If the structure of two such bricks be exam¬ 
ined, the more durable brick will probably show a dense stony-like 
structure, in which the component grains are firmly held by the bond, 
whereas the one with the higher fusion point will probably show a 
crumbly fracture. By reason of these structural differences in the 
bricks the one with the lower fusion point wears away slowly, whereas 
the other, as soon as its surface is worn off, falls to pieces. The com¬ 
position of the latter brick is correct, but the brick was improperly 
made. For this reason, in the selection of a fire brick its analysis 
and fusion point are not reliable indices of its refractoriness. As 
Rigg a has pointed out, the properties possessed by a product that 
may be properly regarded as refractory may include any or all of the 
following, according to the conditions of service: 

1. Absolute infusibility at the highest working temperature. 

2. Complete absence of deformation and shrinkage under working 
conditions. 

3. Mechanical strength. 

4. Complete resistance to penetration of vapors, slags, etc. 

5. A chemical composition fitted to withstand as completely as 
possible the corrosive action of the substances to which the bricks 
are exposed. 

6. Equality and fixity of form and dimensions. 

o Rigg, Gilbert, Defects in refractory brick and their causes: Met. and Chem. Eng., vol. 8, May, 1910. 
p. 237. 




DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 37 

As all of these properties depend on the care with which the bricks 
are manufactured, as well as on their composition, there is obviously 
a good reason for purchasing bricks from firms whose reputation is 
well established and who are able, by reason of their experience, to 
turn out a product that will meet the requirements mentioned by 
Rigg. 

It is well to remember that the structure of a brick—that is, whether 
it is porous or not—has a great deal to do with its fusion point, if it 
is to be exposed to furnace gases or slags. Especially is this true of 
slags; for, obviously, if the brick be porous, the slag will penetrate the 
pores of the brick and will likely act as a flux for its constituents. 
Rigg cites from his own experience an example in point. The melting 
point of a fire-clay mass exposed to a penetrating slag fell from over 
1,700° C. to 1,400° C., although, except for a coat of glaze, the mass 
appeared unchanged. Under the microscope the filling of the pores 
by slag was plainly visible. 

MELTING POINTS OF REFRACTORY MATERIALS. 

The following table shows the melting points of some of the most 
important refractory materials used in furnace construction: 


Melting points of important refractory materials. 


Name of substance. 

Melting point. 

Chemical 

°C. 

0 F. 

nature. 

“Fire cla.v . . 

1,400-1,800 
1,700-1,800 
1,830 
2,040 
2.000 

2,250-3,300 
3,092-3,272 
3,326 
3,704 

Neutral 

Silica. Bridle. 

Acid 

Silica nurfi . 

Do. 


Basic 

Ma tmesia. hrick ... 

3,632 

3,844 

4,060 

Do. 

Alumina. . 

2,100 
2,220 
o 3, 700 

Neutral 

Carhnninrlnm . 

Do. 

Carbon _ . 

a 6, 756 

Do. 






a Boils. 


In Technologic Paper 10 a of the Bureau of Standards the melting 
points of various bricks are given, as follows: 

Melting points of various bricks. 


Kind of brick. 

Melting point. 

° C. 

° F. 

Fire clay. 

1,555-1,725 

2,863-3,169 

Bauxite. 

1,565-1,785 

2,881-3,277 

3,092-3,101 

3,754 

Silica. 

1,700-1,705 

Chromite. 

2,050 

Ma.fmesia. 

2 ,165 

3,993 




a Kanolt, C. W., Melting points of fire bricks: Tech. Paper 10, Bureau of Standards, 1912, p. 16. 

































38 THE electric furnace in metallurgical work. 

As pointed out in the paper by Kanolt above mentioned, “it 
does not seem possible to establish any very definite relation of a 
fire brick, to its melting point. Since the bricks contain about eight 
different constituents in quantities sufficient to affect the melting 
point, and since the melting point may also be affected by lack of 
homogeneity in the material, it is obvious that a prediction of the 
melting point upon the basis of a chemical analysis would be uncer¬ 
tain.’’ 

In brief, it may be said that in the construction of an electric fur¬ 
nace the choice of the refractory material depends on its capability to 
withstand fusion in the walls and the crucible of the furnace when 
subjected to the action of the solids, liquids, and gases that are em¬ 
ployed in connection with or are produced at the working tempera¬ 
ture of the process. 

proper thickness of furnace walls. 

When the kind of refractory material that will be best suited to 
the furnace has been determined, the next item is the most desirable 
thickness of the walls of the furnace, especially of the crucible. This 
detail is of much importance because the efficiency of an electric fur¬ 
nace depends largely on the proportion of the heat value of the elec¬ 
trical energy that is utilized in heating the contents of the furnace. 
This matter is especially important in the electric furnace, because 
the electric energy used in heating the furnace is generally much 
more expensive than are the fuels similarly used. On the other 
hand, as has been pointed out, the heat supplied to a combustion 
furnace is largely carried away by the escaping flue gases, whereas 
in the electric furnace this loss does not occur. Hence in the con¬ 
struction of the electric furnace the main considerations are the heat 
conductivities of the furnace materials and the ratio of heat loss per 
unit of volume. 

Naturally, the heat loss per unit of volume depends largely on the 
heat conductivity of the materials that are used in the construction 
of the furnace. 

heat conductivities of furnace-wall materials. 

In the tabulation following are given the heat conductivities of 
various refractory materials.® 


° Stansfield, A., The electric furnace, 1907, p. 57. 




DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 39 


Heat conductivities of furnace materials. 
[In C. G. S. units.] 


Material. 

Temperature. 

Conductivity. 

Fire-clay bricks. 

_do. 

Alumina bricks. 

Magnesia bricks. 

Lime. 

Carborundum sand. 

Quartz sand. 

Fire-brick dust. 

Infusorial earth. 

—do. 

c C. 

0- 500 
0-1,300 

0- 700 
0-1,300 
20- 98 

18- 98 

18- 98 

20- 98 

17- 98 

0- 650 

0.00140 
.00310 
.00204 
.00620 
.00029 
.00050 
.00060 
.00028 
.00013 
.00038 

-1_ 


In connection with the conductivity figures Stansfield a remarks as 
follows: 

The figures indicate the number of gram-calories of heat that would pass in one 
second through a centimeter cube of the material if the hot and cold sides differed 
in temperature by 1 degree centigrade. The best conductivity varies with the tem¬ 
perature, being greater at high temperatures, as is shown by the first two and the last 
two items in the list. The figures represent the mean conductivity for the range of 
temperature indicated, and were probably obtained by measuring the flow of heat 
through a wall of definite thickness and area, the two sides of which were maintained 
at the temperatures mentioned. It will be understood that a material having a high 
conductivity for heat, as shown in the table, would, if used in the construction of a 
furnace wall, allow a considerable amount of heat to escape and be wasted. 

PROPER VOLUME OF CRUCIBLE. 

After the proper refractory material for use in the construction of 
a furnace has been selected, it is necessary to determine whether the 
laboratory or crucible of the furnace has the proper volume, for the 
latter is largely governed by the heat conductivity of the materials 
used in the construction of the crucible, and likewise the degree of 
heat insulation possible or feasible. On the other hand, it may be 
necessary to provide for carrying away heat from some parts of the 
furnace that may be exposed to corrosive slags or to a very high 
temperature. In order to bring this about, air cooling or water cool¬ 
ing may be adopted. 

INSULATION DESIRABLE. 

If it be desirable to insulate the walls of the furnace, the degree of 
insulation desirable must be determined. To effect perfect insula¬ 
tion would be, as pointed out by Hering , 6 to surround the furnace 
walls with a material that at each point has the same temperature as 
that of the adjacent point of the conductor. In attempting to ob¬ 
tain perfect insulation, it is quite possible to overinsulate, and thus 
cause serious damage to the inner walls of the crucible; that is, in 

o Stansfield, A., loc. cit. 

b Hering, C., The thermal insulation of furnace walls: Met.andChem. Eng., vol. 10, February, 1912, p. 97. 

44713°—Bull. 77—16-4 





















40 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


certain instances, in order to maintain the inner walls it may be 
necessary to permit a considerable flow of heat from the inner walls 
through the outer walls in order to prevent the destruction of the 
inner walls. The degree of insulation that should be attempted can 
be determined only by careful calculation and experimentation. 
The following table of insulating values is given by Snyder.® 

Thermal conductivity of refractories~ 


D—Degrees centigrade required to force a heat flow of 1 kilowatt per square foot 
through 1 inch of thickness of the material. T—Temperature at hot side of material, 
t—Temperature at cold side of material. 


Alumina brick. 

Ashes, wood. 

Brick dust, coarse. 

Carbon, retort, solid. 

Carbon, electrode. 

Carbon, electrode. 

Carbon, electrode. 

Carbon, electrode. 

Carborundum sand. 

Cement. 

Charcoal. 

Clinker, small grains. 

Coke, powdered. 

Copper, metallic. 

Fire brick. 

Fire brick. 

Fire brick. 

Fire-brick dust. 

Graphite, dust. 

Graphite, electrode. 

Graphite, electrode. 

Graphite, electrode. 

Graphite, electrode. 

Infusorial earth. 

Infusorial earth. 

Iron, metallic. 

Lime. 

Magnesia, brick, dust. 

Magnesia, brick. 

Magnesia, calcined, Grecian, granular 

Magnesia, calcined, Styrian. 

Magnesia, calcined, light, porous. . . . 

Quartz sand. 

Silica brick, burned to 1,050° C. 

Silica brick, burned to 1,310° C. 


t T D 


0 

700 

320 

0 

100 

3, 840 

0 

100 

1,680 

0 

100 

45 

100 

400 

7.1 

100 

800 

5.2 

100 1,200 

5.0 

100 1,600 

4.5 

18 

98 

1, 300 

0 

700 

3, 800 

0 

100 

2, 960 

0 

700 

600 

0 

100 

1,480 

0 

30 

0.7 

0 

500 

465 

0 1,000 

155 

0 1,300 

105 

20 

98 

2, 300 

20 

100 

1, 630 

100 

400 

1.9 

100 

800 

2.1 

100 1,200 

2.3 

100 1,600 

2.5 

17 

98 

5, 000 

0 

650 

1,720 

100 

200 

4.4 

20 

98 

2,250 

20 

100 

1, 300 

0 1,000 

92 

20 

100 

1,450 

20 

100 

1,920 

20 

100 

4,100 

18 

98 

1,090 

0 1,000 

330 

0 1,000 

210 


As has been stated, the ratio of heat loss per unit of volume will 
be inversely proportional to the dimensions of the furnace when the 
walls are of equal thickness in each furnace considered. However, 


a Snyder, F. T., Flow of heat through furnace walls: Trans. Am. Electrochem. Soc., vol. 18, 1910, p. 243. 








































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 41 

as a matter of tact, smaller furnaces generally have thinner walls 
than clo the larger ones, and so, in addition to the heat loss that may 
be calculated as being inversely proportional to the dimensions of 
the furnace, the loss of heat through correspondingly thinner walls 
must be considered. For this reason a large furnace is more efficient 
than a small furnace; that is, the amount of work performed per unit 
ol electrical energy expended is greater in the large furnace than it is 
in the small one. As Stansfield® has pointed out, “in the extreme 
case of a small furnace constructed as an exact model on a scale of 
1 inch to the foot of a large furnace, the heat loss for each cubic inch 
of the model would be 144 times as great as from the large furnace, 
provided, of course, that both attained the same temperature. In 
other words, if the furnaces were merely being kept hot, no work 
being done in them, the small furnace would need 144 times as much 
heat per cubic inch as the larger furnace in order to keep it heated 
to the same temperature.” 

In some electric-furnace processes, as making carborundum by the 
Acheson furnace, it is possible to develop the heat within the charge 
being heated and to interpose between the hot inner part of the charge 
and the exterior walls of the furnace enough charge to prevent the 
exterior walls from being heated. Generally such processes are not 
continuous and the outside of the charge is not attacked. Naturally 
the ideal condition in electric-furnace work is to have the process 
continuous, with the cold charge advancing from the cold exterior 
part of the furnace to the hot interior part. In this way, of course, 
the heat radiating from the center of the furnace is absorbed by the 
cold charge advancing toward the center and is not lost, as it is when 
it is dissipated through the furnace walls by conduction and radiation. 
There are mechanical difficulties that interfere with the successful ac¬ 
complishment of such a scheme, but the nearer it can be approached 
the greater will be the efficiency of the furnace and the process. 

ELECTRODES. 

Electrodes serve to carry current into furnaces in which electrical 
energy is converted in part to heat energy, and as the electrodes 
are the only avenue through which current is introduced into the 
charges, it is important that they should neither contaminate the 
charges nor cause undue waste of energy. They are made in various 
shapes and sizes to suit particular conditions, but the essential 
properties are common to all. 

An electrode should possess high electrical and low thermal con¬ 
ductivity. It should be resistant to atmospheric oxidation and 
capable of withstanding handling and temperature changes without 
danger of breakage. 


a Stansfield, A., The electric furnace, 1907, p. 58. 




42 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

Electrodes for use in electric furnaces are commonly divided into 
two classes, carbon and graphite electrodes. Metallic electrodes are 
employed in rare instances. 

Carbon electrodes are made from such materials as petroleum 
coke (the ultimate residue in the distillation of petroleum), retort 
carbon (a pure form of carbon deposited in coal-gas retorts), and 
anthracite. 

MANUFACTURE OF ELECTRODES. 

The process of manufacture is simple. The material is highly 
heated in a retort to remove volatile matter, pulverized, mixed with 
a binder, formed in a press, and baked in a kiln. Graphite electrodes 
are simply amorphous-carbon electrodes that have been artificially 
graphitized in an electric furnace, and are thus a product of the elec¬ 
tric furnace. Many of the difficulties and annoyances in the opera¬ 
tion of large electric furnaces were until recently due to the breaking 
of poor electrodes. To-day strong electrodes may be had 24 inches 
in diameter, whereas only a few years ago none over 12 inches had 
the required strength. 

CARBON COMPARED WITH GRAPHITE ELECTRODES. 

There is no simple arbitrary rule by which to determine whether a 
carbon or a graphite electrode is the more suitable for any furnace. 
It is generally conceded that the graphite is more resistant to chemi¬ 
cal action, and in particular to atmospheric oxidation. Moissan 
determined the temperature at which various forms of carbon begin 
to oxidize. According to him, amorphous carbon begins to oxidize 
at a temperature as low as 375° to 490° C., and graphite does not 
oxidize appreciably below 665° to 690° C. In practice, however, it 
is less apparent that graphite is inherently superior to carbon elec¬ 
trodes as regards oxidation. That the carbon electrode has the lower 
heat conductivity has been established by various workers in both 
experiment and practice. According to Wolgodine’s® research, the 
comparative conductivities of graphite and carbon expressed as 
temperature drop in centigrade degrees per kilowatt flow per square 
foot through a 1-inch thickness of material, are as follows: Graphite 
electrode, 2.3; carbon electrode, 4.7. 

ENERGY LOSS IN ELECTRODES. 

The total energy loss in electrodes is the sum of the loss due to the 
resistance offered to the passage of the current and the loss by con¬ 
duction of heat away from the interior of the furnace. This amounts 
to about 8 per cent of the total input, and when cooling water is used 
this may account for another 3 per cent. The net efficiency of an 


a Wolgodine, S., and Queneau, A. L., Conductivity, porosity, and gas permeability of refractory mate¬ 
rials: Electrochem. and Met. Ind., vol. 7, 1909, p. 383. 



DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


43 


electrode, therefore, concerns both its electrical and its thermal 
conductivities. The electrode efficiency is consequently a physical 
characteristic for any electrode material, but varies in accordance 
with the relative importance of the electrical and thermal factors 
when the quality of the current impressed is varied. 

EFFICIENCY OF ELECTRODES. 

In general, the net efficiency is increased by producing the necessary 
wattage with as low a current and as high a voltage as possible. The 
difference in net efficiency of carbon and graphite electrodes need 
be only a few per cent. As graphite is a better conductor of elec¬ 
tricity than carbon, the C 2 R loss (C— capacity; R = resistance) is less 
in a graphite electrode than in a carbon electrode. The conductivity 
of graphite is usually taken as being four times that of carbon. 

CONDUCTIVITY OF ELECTRODES. 

The conductivity increases with increasing temperature. Misselt® 
estimates that in general the thermal conductivity of insulating 
materials decreases at the rate of 1/273 part for each degree above 
0° C. Small electrodes can be loaded more than large ones, possibly 
owing to the greater closeness with which the particles are packed. 
In view of this fact, modern factories have adopted increasingly larger 
presses in order to reduce this discrepancy and improve the larger 
sizes. Again, for the same composition, the specific resistance of 
round electrodes is much less than that of those with square cross 
sections. As to the ultimate sizes that can be produced, little can be 
said. As before stated, although the largest electrodes of sound 
quality formerly on the market were 12 inches in diameter, it is now 
possible to get them up to 24 inches without difficulty. Nevertheless, 
as has been pointed out by one writer on this subject, it may be 
doubted whether sizes will go on increasing, for the specific conduc¬ 
tivity as well as the mechanical strength tends to decrease, whereas 
the difficulties in handling increase. Attempts have been made to 
increase the conductivity of electrodes by introducing metals, such as 
pure iron, with the carbon material while it is being molded. It is 
stated that the resistance thus formed can easily be reduced to one- 
half the ordinary value with comparatively little metal. 

ESSENTIALS IN USE AND DESIGN OF FURNACE ELECTRODES. 

As stated by Hering, 5 the lav T s of electrode losses are: 

1. The combined loss through the cold end of an electrode is 
equivalent to the sum of the loss by heat conduction alone (when 

a Misselt, W T ichelto, Zeitschr. Ver. deut. Ing., June, 1908, p. 90. 

b Hering, C., Laws of electrode losses in the electric furnace: Electrochem. and Met. Ind., vol. 7,1909„ 
pp. 442, 514. 




44 THE ELECTBXC FUENACE IN METALLUBGICAL WOBK. 

there is no current) and half the PR loss (7=rate of flow; R = resist¬ 
ance). 

2. This combined loss will be least when the loss by heat conduction 
alone is made equal to half the PR loss; the total loss will then be 
equal to the PR loss, and no heat will be conducted from the interior 
of the furnace. 

3. This minimum loss is dependent only on the material, current^ 
and temperature, but not on the absolute dimensions; it merely 
fixes the relation of the cross section to the length, but leaves a choice 
of either; hence 

4. For economy of electrode material the electrode should be made 
as short as practical considerations permit. 

5. For each material there is a definite minimum loss of electrode 
voltage which depends only on the temperature and is independent 
of the dimensions or the normal current for which the furnace is 
designed; hence 

6. The best possible electrode efficiency for any material may be 
determined from the total voltage of the furnace and this minimum 
voltage due to the material and the temperature, and is independent 
of the dimensions. 

7. The temperatures indicated by the heat gradient of the com¬ 
bined flow are equal to the sums of those of the individual flows. 

The proof of these laws is given in a paper by Hering on “Laws of 
Electrode Losses in Electric Furnaces and need not be repeated 
here. 

The fundamental principle involved is the one Hering announced 
in 1909, namely, that no heat should leave or enter the furnace 
through the electrode, or, in other words, that the heat generated by 
the electrical resistance shall raise the temperature of the hot end to 
that of the furnace; it is shown that under the given conditions this is 
also the condition of least total loss. 

WATTAGE AS A MEASURE OF FLOW OF HEAT. 

Before giving the formulas, Hering explained that it simplifies such 
calculations greatly to represent and measure a flow of heat in terms 
of the electric unit, the watt, instead of in calories per second. He 
stated that a watt is just as correct a measure of a flow of current of 
heat (calories per second) as an ampere is of the flow of electric cur¬ 
rent (coulombs per second). Heat is a form of energy, and the rate 
of flow of heat p.er second is power, hence it is measurable in units of 
power, such as watts. Since Hering called attention to this point 
others have endeavored to improve matters by calling this unit 
“watt-seconds per second/’ but this cumbersome name is entirely 
unnecessary and obscures rather than simplifies one’s conceptions. 


a Hering, C., Trans. Am. Electrochem. Soc., vol. 16,1909, p. 265. 




DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 45 

• 

It is evident that watts X seconds -f- seconds = watts. When the heat 
conductivity of a material is given as 10 watts for an inch cube, it sim¬ 
ply means that with a 1° C. difference of temperature between two 
pai allel sides, and perfect heat insulation on the other four, the same 
amount of energy will flow through as heat, say into water at the cold 
end, as would enter the water from a coil of resistance wire in which 
10 watts were being set free. 

Foi these reasons, in the following discussion, quoted from Hering a 
all flows of heat are represented in watts. Hering recommends that 
all thermal constants pertaining to electrodes be given in terms of 
watts instead of calories per second. The conversion factors are: 
Gram-calories per second X 4.18617 = watts, and watts X 0.238882 = 
gram-calories per second. The abstract from Hering follows: 

FORMULAS. 

The value of the symbols used in the following formulas are the same whether inches 
or centimeters are used, providing they are employed consistently throughout, includ¬ 
ing all those constants which are based on dimensions, and which of course will be differ¬ 
ent; those like the electrode voltage or watts per ampere are, of course, the same in 
both systems. All of the formulas in which the following symbols are used are in terms 
of actual units and may therefore be used directly in practice. 

Let 8 , =cross section in square inches. 

L=length in inches (the essential length). 

J=current in amperes. 

TF=watts generated electrically in the electrode. 

iZ'=heat flow in watts which would flow if there were no current. 

^=heat flow in watts wdiich enters the hot end from the furnace. 

X=heat flow in watts leaving the cold end. 

T= temperature drop in centigrade degrees between the hot and cold ends. 
r=electrical resistivity in ohms, inch cube units. 

£=thermal conductivity in watt, inch cube units. 
e=electrode voltage in volts. 

i£=total voltage between the two ends, or the watts per ampere. 
s=specific cross section in square inches. 

8 ,/ =section in square inches per ampere per inch of length (or in square centi¬ 
meters per ampere per centimeter length if the other quantities are in 
terms of centimeters). 

DETERMINATION OF PROPER SIZE OF ELECTRODES. 

The underlying feature is that the electrode shall not chill the furnace nor develop 
a high temperature point within the walls at which the temperature is greater than in 
the furnace. Hence the hot-end temperature should be as nearly as practicable equal 
to that of the furnace. 

The current and furnace temperature are always given in the specifications. The 
material and either the length or the section (but not both) may also be specified, but 
preferably all three should be left to the designer. The voltage and loss can not be 
specified, as they are determined by the current, temperature, and material. 

The length (that is, the essential length, not including additions to either or both 
ends for other purposes than to get the energy through the walls) may be determined 
solely by the thickness of the furnace walls; but as this affects the cross section, some 


a Hering, C., loc. cit. 





46 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


latitude should be left in case the corresponding section is found to be too large or too 
small to be practicable. 

The section in square inches is then determined at once by multiplying the proper 
temperature value of S' from the table [“constants for calculating electrodes”] by the 
current in amperes and by the length in inches. Formula: S—ILS'. If this is too 
large or too small to be practicable, the length may be changed and the section may 
be redetermined. The quotient of the section divided by the length is a constant for 
any specified conditions (numerically equal to S' from the table multiplied by the 
current), hence they may both be increased or decreased in the same proportion. 

Should this table of values not be available and the specific section be known, for¬ 
mula S=ILs-y/ 7 T should be used for calculating the section. If this is also not known, 
then use the conductivities in the formula S=IL~\Jr-±-2k T. Great accuracy is not nec¬ 
essary when one is near the correct result, as an error in section near that point pro¬ 
duces a relatively much smaller error in the loss. 

The loss in the electrode in "watts is entirely independent of the section or length 
adopted, provided only that their quotient is approximately as above. It is calcu¬ 
lated in watts by multiplying the corresponding temperature value of E in the table 
by the current (formula mX—IE ). If this table is not available, we may use the elec¬ 
trode voltage in the last part of formula mX=2H= W=I^j2krT—Ic-yJ T. If this is not 
available either, then use the conductivities in the preceding expression of this 
formula. This loss is for one electrode and it is the least possible under those condi¬ 
tions. 

Constants for calculating electrodes. 


Tempera¬ 

ture. 

E. 

(Watts per ampere.) 

S'. 

(Square inches per ampere 
per inch iength.) 

S'. 

(Square centimeters per ampere 
per centimeter length.) 

°C. 

°F. 

Car¬ 

bon. 

Gra¬ 

phite. 

Iron. 

Cop¬ 

per. 

Car¬ 

bon. 

Gra¬ 

phite. 

Iron. 

Cop¬ 

per. 

Car¬ 

bon. 

Gra¬ 

phite. 

Iron. 

Copper. 

400 

752 

1.00 

0.85 

0.145 

0.095 

0.00165 

0.00040 

0.000103 

0.000016 

0.0042 

0.00100 

0.00026 

0.000041 

600 

1,112 

1.38 

1.04 

.225 

.140 

.00114 

.00031 

.000102 

.000015 

.0029 

.00078 

.00026 

.000037 

800 

1,472 

1.68 

1.19 

.295 

.184 

.00090 

.00027 

.000101 

. 000014 

.0023 

.00068 

.00025 

.000036 

1,000 

1 832 

1.93 

1.32 

.350 

.226 

.00076 

.00024 

.000098 

. 000014 

.0020 

.00061 

.00025 

.000036 

1,200 

2,192 

2.15 

1.43 

.410 

.270 

.00069 

.00022 

.000094 

. 000014 

.0018 

.00056 

. 00024 

.000035 

1,400 

2,552 

2.36 

1.52 

.460 

.310 

.00062 

.00020 

.000092 

. 000014 

.0016 

.00051 

.00023 

.000035 

1,600 

2,912 

2.53 

1.62 

.510 

.351 

.00057 

. 00019 

.000089 

.000014 

.0014 

.00018 

.00023 

.000035 

L800 

3,272 

2.68 

1.71 

.565 

.391 

.00053 

.00018 

.000087 

.000014 

.0013 

.00046 

.00022 

.000035 

2,000 

3,632 

2.83 

1.79 

.610 

.430 

.00049 

.00017 

.000085 

.000014 

.0012 

.00044 

.00021 

.000035 


When the current for a furnace varies appreciably, the calculations must of course 
be made for some assumed normal value, remembering that whenever it is less than 
that the electrode will chill the furnace more or less; and whenever it is greater the 
electrode will get hotter within the walls and in both cases the total loss will be 
greater. 

In operating a furnace, if the electrode is found to chill the product it is either too 
short or too large in section. If, on the other hand, it is found to produce excessive 
temperatures within the walls, it is too long or too small in section. The current 
density is not a determining factor. 

The hotter the outside terminal is allowed to get, the smaller the loss, but the 
larger the section or shorter the electrode. 

When the proportions turn out to be large in section and short in length the relative 
proportions may be improved by increasing both length and section. On the other 
hand, if the electrode is abnormally long and small in section (as for instance with iron 
or copper and small currents), then if the section can not be made smaller, there seems 
to be nothing left to do except to sacrifice some of the loss by making the electrode 
shorter and it will then chill the furnace more or less. 





































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 47 


The additional lengths of the electrode necessary for the terminals, for feeding, or 
for the distribution of the current in the inside, must be calculated separately; as 
they are determined by entirely different laws and conditions; the above refers only 
to the essential part which is necessary to get the current into and out of the furnace 
as well as possible. The above length must, therefore, never include the long exter¬ 
nal part outside the furnace for feeding purposes. Such a part radiates heat to the 
air, and therefore follows entirely different laws of proportions. A redeeming feature 
of such a case is that the outside temperature used to determine the proportions of 
the essential part, may be allowed to be very high, probably limited chiefly by oxida¬ 
tion, thereby reducing the total loss which has been increased by the long external 
part. 

PROPER CONSTRUCTION OF ELECTRODE HOLDERS. 

HEAT SOCKETS AND CLAMPS. 



When the current is fed into the end of the electrodes, as in some 
carbide and ferro-alloy furnaces, the connections are applied by 
means of heat sockets whereby they are frequently attached once 
for all. The other 
method is to use 
clamps which permit 
the electrode to be 
passed through them, 
their clutches being 
merely pressed tightly 
against the smooth 
hard furnace elec¬ 
trode. 

The latter is pre¬ 
ferred as a means of 
conducting the cur- 

. . i , i Figure 14 .— Trollhattan electrode before and after use. Old type 

rent to the electrode, of holder 



owing to the fact that 

thus it is possible to place the “electrode holders” immediately on 
the roof of the furnace and keep them stationary. This arrangement 
permits the introduction of the current as close as possible to the end 
of the electrode where it enters the charge, so that less energy is spent 
in overcoming the resistance of the electrodes themselves than when 
the current is introduced at the end of the electrode. The connec¬ 
tion between the cables and bus bars carrying the current to the 
furnace, and the electrodes, which, as before stated, serve to carry 
the current into the furnace, is made by electrode holders. These 
holders for convenience may be divided into two classes, namely, top 
holders and side holders. 


TOP HOLDERS. 


With top holders the current is introduced at the top of the elec¬ 
trode through a holder such as is shown in figure 14. The holder at¬ 
tached to the end of the electrodes is also shown in figure 15; and, 









































48 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

as will be noted by reference to the figure, the same contact surface 
is maintained between the holder and the electrode until the electrode 
is used up. Top holders are generally used in open-top furnaces, 
such as the ferrosilicon and carbide furnaces, and in all furnaces in 
which a frequent raising and lowering of the electrode is necessary. 
If the electrode as a whole is subjected to erosion from any cause, it is 
then practically necessary to use a top holder, owing to the fact that 
the uneven surface produced by the erosion would prevent a quick 
and effective fitting of the electrode holder to the electrode, espe¬ 
cially after the electrode became hot, and the proper contact between 
the holder and the electrode is, as can be readily understood, of great 
importance. 

SIDE HOLDERS. 

Side holders are generally used on closed-top furnaces or on con¬ 
structions in which the electrode above the holder will not be sub¬ 
jected to sufficient heat to bring about its oxidation and thus cause 
it to have an irregular surface. Electrodes used with side holders 
must be of fairly uniform dimensions. For this reason, graphite elec¬ 
trodes are better adapted for use for side holders than are amorphous- 
carbon electrodes, as they are more easily machined. This is espe¬ 
cially true where it is desired to keep the top of the furnace not 
only closed but tight, as for example in the Swedish and California 
types of iron reduction furnaces. In these types of furnaces the 
electrode holder is placed on the roof of the crucible, for in this 
way the current is conducted into the electrode at a point where 
it will have the shortest distance to travel before it reaches the 
point where it does its work, and in this way the electric- 
energy loss that may be due to the resistance of the electrode is 
reduced. Then, too, it is to be remembered that the ohmic resistance 
of carbon decreases with increasing temperature, and as the hottest 
part of the electrode will be that part that extends down into the 
furnace, the ohmic resistance of the electrode is reduced to a minimum 
by getting the holder as near the hot end of the electrode as possible. 
The side holder permits of the joining of one electrode to the other 
without the removal of the holder, an arrangement that is, of course, 
decidedly advantageous. 

ESSENTIAL DETAILS OF HOLDERS. 

In the construction of electrode holders all current-carrying parts 
are usually of copper or bronze, the main posts and supports being 
of steel. A current density of from 19 to 30 amperes per square inch 
is usually adopted for the current-carrying contact parts, the lower 
limit being preferred. 

As before stated, the surface condition of the electrode is of the 
greatest importance, so far as the making of a good contact between 


DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


49 


the holder and the electrode is concerned. If the contact is not a 
good one the holder becomes hot and may even be ruined. On small 
furnaces not equipped with water-cooled holders it is especially neces¬ 
sary to have a good contact between the holder and the electrode, 
and so elastic layers of copper netting, thin iron sheets, or something 
of the kind, is used to insure a good contact. Efficiency, of course, 
demands a good contact between the electrode and the holder, even 
if the holder be water-cooled, for although the water cooling may 
prevent the holder from becoming excessively hot, the heat developed 
is at the expense of electrical energy, and is simply carried away by 
the cooling water without having done useful work. Then, too, a 
bad contact is likely to cause the electrode itself to become red-hot 
adjacent to the holder, and thus cause a serious deterioration of the 
electrode, due to burning; and the excessive heat from the electrode 
may cause a water-cooled electrode holder to crack or break, and because, 
as before stated, ohmic resistance decreases with increasing tempera¬ 
ture, the flow of current 
will be greatest through 
the hot part of the elec¬ 
trode and will cause this 
hot part to become still 
hotter. 

As illustrating the im¬ 
portance of using the best 
type of electrode holder 
possible, the following 
figures are taken from an 


n 



Y 


7 


Figure 15. —Specially shaped electrodes for electric furnaces. 


article that appeared in “ Stahl und Eisen,”° a translation of which 
has been published in Metallurgical and Chemical Engineering. 


In a large plant producing 4,000 tons of ferro-alloys per year the cost of maintenance 
of the holders was marks 6.40 ($1.60) per ton of metal produced, or marks 25,600 ($6,400) 
per year. By using an improved holder this cost was reduced to marks 1.60 ($0.40) 
per ton, saving marks 19,200 ($4,800) annually. The consumption of electrodes was 
also reduced, resulting in an additional saving of marks 12,800 ($3,200). The total 
saving due to the use of an improved holder was, therefore, marks 32,000 ($8,000), or 
marks 8 ($2) per ton of product. 


SPECIALLY SHAPED ELECTRODES. 


Owing to the fact that it is important to effect the proper contact 
between the electrode holder and the electrode, it was rather common 
practice to shape the ends of the electrodes to fit the holders, espe¬ 
cially where top holders were used, and as good amorphous carbon 
is generally difficult to machine properly, the particular shape desired 
was given to the electrode before baking. Some of these special 
shapes are shown in figure 15. 


a Anon., Die Electrodenfassungen bei Electroofen: Stahl und Eisen, vol. 33,1913, pp. 472-478, 555- 
561. Translated by Kennedy, A. E., Electrode-holder construction for electric furnaces: Met. and 
Chem. Eng., vol. 11, June, 1913, p. 321. 
































50 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


TYPES OF TOP HOLDERS. 


The subject of electrode holders has been discussed in 11 Stahl und 
Eisen/’ a and a translation of the article has been published in 
Metallurgical and Chemical Engineering. 6 The following lengthy 
quotation from this translation is given here: 



In carbide plants the connection shown in figure 16 was formerly often used, con¬ 
sisting of two solid V-shaped cast-iron clamps a, tightened by bolts b, and connected 

to the cables by means of necks c and pressure 
plates d. This solid electrode holder never proved 
satisfactory. When the electrode became short 
the holder as well as the electrode became hot and 
the cast-iron pieces often melted. Later on, a cool¬ 
ing device was combined with this construction, as 
shown in figures 17 and 18. 

Figure 19 shows a connection that has proved 
satisfactory in a carbide furnace. The head of the 
electrode is dovetailed and clamped between two 
cast-iron plates b by means of two weights a. The 
whole apparatus is supported by an iron structure 
which itself hangs on an electrically insulated 
hook. Copper plates d, e, and / serve to make con¬ 
tact at h with the flexible laminated ribbons g , carry¬ 
ing the current. The mechanical suspension is 
independent of the electric connection, and the 
weight of the electrode tends to tighten the contact 
between copper plates and electrode head. An 
electrode equipped with this holder can be put 
into service very quickly by hooking into the 
chain of the windlass and making contact at h. 

The holder shown in figure 20 has been successful 
in the manufacture of ferro-alloys. The electrode 
consists of four carbon blocks embedded in a 
tamped carbon mixture. Two opposite surfaces of 
the same block have dovetailed recesses in order 
to clamp the copper plates a by means of the screw 
bolts b and the plates c. This holder is simply 
connected to the plates d of the current load e. The 
plates a preferably consist of copper,'the plates c of steel casting, the pressure screws 
of iron with square threads, and the plates d of bronze or of cast iron containing 
manganese. 



Figure 16.—Holder formerly used with 
carbide furnaces. 


If the surface of the dovetails is not smooth enough to secure a good contact, the 
heating at the contact will be avoided by putting a cushion of very fine strands of a 
copper cable between the carbon and the copper plate. Under the pressure of the 
screws this cushion of about 0.5 cm. (-^g- inch) thickness is pressed into the rough spots 
of the carbon and secures the passage of the electric current under favorable conditions. 

When the electrode butts are to be utilized down to a length of 50 cm. (20 inches) it 
becomes necessary to cool the parts artificially to prevent the holder from being 
destroyed by the heat of the furnace. Figure 21 shows the copper plates of the current 
lead being wedged to the carbon by means of water-cooled channels, a, open at the 
top. This design has given good results, especially in furnaces with an open hearth. 


a Anon., Die Electrodenfassungen bei Electroofen: Stahl und Eisen, vol. 33, 1913, pp. 472-478, 555-^561. 
b Issue of June, 1913, pp. 321-324. 

















































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


51 



Figure 17.—Electrode holder with cooling device. 



































































































































































































52 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


The holder shown in figure 22 is good for cylindrical electrodes. The flexible leads 
are fastened to a bronze piece, a, of special form. This piece is fastened to the carbon 

by an electrically insulated 
ring and has a contact surface 
machined on the lathe. The 
holder itself is a box, c, sur¬ 
rounding the head of the elec¬ 
trode and pressed to the piece 
a by the screws b. After loos¬ 
ening the screws b, the pieces 
a and c can be taken apart by 
a quarter turn. The piece c, 
which is protected by the iron 
sheet d, is put on top of the 
electrode, and bronze, e, is 
poured into the free space be¬ 
tween the box and the carbon 
and on top of the electrode. 

The weight of the electrode 
produces an excellent contact 
between the bronze and the 
walls of c. The holder is 
cooled with water which 
enters through /, and drops 
through the central overflow 
pipe onto the top of the elec¬ 
trode; the admission of water 
is regulated to make up for 
evaporation. 

Figure 23 shows a holder 
cooled by water under pres¬ 
sure. The ring-shaped piece 
a is hollow in the center, the 
water circulating through b. 
Copper sheets, c, serving both 
as mechanical suspension of 
the electrode and as current 
leads, are pressed against the 
electrodes with cast-iron or 
bronze wedges, d. The wedges 
have regulating screws, and 
piece a is held by four pres¬ 
sure screws. 

While an intimate contact 
is hard to make between a car¬ 
bon electrode and the cable, it 
is easily obtainable between 
the cable and a metallic elec¬ 
trode by screwing the pole 
shoe at the end of the cable 
to the electrode. The contact 
surfaces of the pole shoe and 
of the electrode can be ground into each other, which warrants a good contact on the 
entire surface. As it is hardly ever possible to get the surface of a nonmetallic electrode 







































































































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 53 

perfectly plane there will always be a certain contact resistance and evolution of heat 
and it may be necessary to remove this obnoxious heat of the contacts by special con- 
tact-cooling devices. 

The Westdeutsche Thomas Phosphatwerke have a German patent (No. 207,361) for 
the construction shown in figure 24. The square-shaped electrodes a have a recess on 
top, and a copper cap c is dumped over this head. In order to make good contact where 
the surfaces do not touch each other, the cap is filled with liquid aluminum or another 
metal of high melting point, and while the aluminum (or other metal) is still liquid a 



Figuee 19.—Detailed views of electrode holder satisfactorily used in carbide furnaces. 


red-hot wrought-iron ring e is shrunk around the copper cap. By the simultaneous 
gradual cooling of the aluminum and the iron ring a very close contact is produced 
between the copper cap, the aluminum layer, and the top of the electrode. 

Contact resistances can not show up any more. The pole shoe /, the screws g, the 
hoops l, and the cable ends can be seen from the figure. As no soldering is required 
in this design, an important source of trouble is eliminated. 

With the patterns of holders described so far, the remaining butt of the electrode, 
which is about 50 cm. (20 inches) long in furnaces with an open hearth, is not used. 













































































































































54 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 




v 



Figure 20.—Another type of electrode holder satisfactorily used in carbide furnaces. 





























































































































































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 55 

In furnaces with arches, as for instance, in electric steel furnaces, the discard is larger, 
leaving a butt of about 90 cm. (36 inches), which means that only about one-half of the 
electrode can be used. 

MOVABLE SIDE HOLDERS. 

In order to utilize completely the electrode material, movable holders are employed 
which allow the electrodes to slide through. The electrode is not held on one end, but 





Figure 21. —Water-cooled electrode holder. 

somewhere between its two ends connection is made to the cable) when a piece of 
electrode is used up, another piece of carbon is added to the previous piece, and the 
holder raised accordingly. 

Figure 25 represents this type of connection in a design proposed by Louis. The 
electrode is held between two hollow pieces of metal, a, which form a pair of tongs. 


44713°—Bull. 77—16-5 

















































































































































































56 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


The tongs are pressed against the electrodes by the screw b. W hen the lower part of 
the electrode is consumed, it can be fed downward for the desired length. The cable 
is fastened at c; the best way of cooling the pieces a and the contact is by means of 
water under pressure. 




Figure 22.—Holder for round electrode. 


Figure 26 shows another tongs design for a combined electrode of several blocks. 
The carbon blocks are pressed by steel levers by means of the screws a against the 
central piece of bronze, which serves as suspension and current lead. 

Figure 27 shows a similar design in which adjustable wedges are employed which are 
water cooled. 























































































































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 57 

The holders of most electric steel furnaces are built for complete consumption of the 
electrode material and have been repeatedly shown to our readers. 

In the Heroult furnace each electrode is held by a bracket from a vertical rack, which 
is moved up and down by gear and pinion. Each carbon is surrounded by a band of 
metal, pieces of copper being inserted, which carry the current from the cables. 

Figures 28 and 29 show various constructions used by the Aktisbolaget Elektrometall 
Ludwika, and by Nathusius. 



Figure 23.— Electrode holder cooled with water under pressure. 
METALLIC CONDUCTORS IN ELECTRODE HEADS. 


Keller’s method of inserting the metallic conductor into the head of the electrode 
gives satisfactory results. This method has been known for some time. With small 
electrodes the connection to the current leads is obtained by means of metallic plates 
between the conductor and the carbon. But too close a tightening of the bolts often 
causes the electrode to crack whereas otherwise the contact may be poor. 

Figure 30 shows an electrode connection often used for the manufacture of aluminum. 
The end of a flat piece of iron is upset in the shape of a fishtail and then molded into the 










































































































58 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 



electrode. Plants who manufacture their own electrodes insert this connector before 
baking, whereas those who buy them baked fasten the metal with a graphite mortar or 
by pouring liquid bronze into the hole. 

Figure 31 shows a connection made by a screw bolt. A thread is made in the end of 
the electrode, and an iron rod, threaded at one end, is fastened in the same. A mantle 
of bronze or aluminum bronze forms contact at both ends and secures the passage of 
current. Four or six of these electrodes are sometimes combined in aluminum furnaces, 
as shown in figure 32. 

A connection of Dr. Lessing, of Nuremberg (German patent 211,273), is shown in 
figure 33. It consists of a piece of iron molded with the electrode which has square¬ 
shaped threads of such an angle that the distance b between the threads is considerably 

larger than their thickness a. This bolt 
can be removed from the carbon before 
baking without destroying the threads in 
the latter. The iron piece d connects 
with the threaded bolt c. By screwing 
the bolt into the carbon and securing it by 
a countemut, e , an excellent contact is 
obtained. 

Keller allows the metallic conductor a 
certain play, the lower end being tapered 
thicker into the hollow top of the carbon 
(German patent 218054; fig. 34). Liquid 
metal, copper or pig iron, is then poured 
into the space left in between. This 
produces a mechanically and electrically 
reliable contact. No jaws, wedges, or 
screws are required to make or improve 
the contact. The interior of the metallic 
conductor is intensely water-cooled in 
order to utilize as much length of the elec¬ 
trode as possible. The metal has to be 
poured carefully into the open gap 
between conductor and carbon. The 
cavity in the electrode is first heated by 
a piece of red-hot iron, the preheated 
current conductor is then introduced and 
kept about 5 mm. (0.2 inch) distant from 
the bottom of the cavity by a small, hard 
body. Very hot bronze or cast iron is 
then poured in. 

Although the metal shrinks a little, it 
makes an intimate contact. The effect of 
shrinkage can be entirely overcome by casting about 30 grams of tin around the con¬ 
tact metal after it has cooled. If the contact should not be perfect, it heats up when 
the electrode is put to use, the tin melts and flows into the interstices and makes a 
perfect contact. The costs of this method are said to be low. The contact metal and 
the tin can be recovered after the electrode has been consumed. 

This type of connection is mechanically strong, and its electrical resistance is low. 
As the cooling effect reaches clear down into the bottom of the cavity in the electrode, 
the contact will not soften, even when it is heated by the proximity of the arc. The 
electrode can, therefore, be introduced through the roof of the furnace and be used up 
to an extremely small rest piece. As no part of the metallic conductor is wider than 



Figure 24.—Electrode holder used in Germany. 





















































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES 


59 


the electrode, it can pass through the same opening which fits closely around the carbon 
and can be packed in firebrick up to the diameter of the electrode. This method is 
satisfactory for single electrodes, as well as for bundles of them. 





Figure 25. —Electrode holder with movable contact. 

The advantages of Keller’s connection are: 

1. It avoids all intermediary contacts between the current cable and the carbon. 

2. It avoids all parts extending beyond the area of the electrode, and has no brack¬ 
ets, screw bolts, wedges, etc., which are liable to deteriorate and cause a high main¬ 
tenance cost. 













































































































































































60 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


-E31 


. / 
*•: / 
/ 




-£Z?\ 





3. It requires no finishing of the electrode surfaces or of the metallic conductor. 
There is even a certain advantage in leaving the walls of the cavity roughly finished, 
as it improves the contact surfaces and the mechanical strength of the joint. 

4. The electrical contact is perfect, as the liquid metal fills all the free spaces. 

5. The mechanical connection is strong and fool-proof, even when the carbon is 
almost used up. 

6. The cost of maintenance is low. 

7. The electrode can be used down to below 25 mm. (less than 1 inch) length, which 
dispenses with the cumbersome joining of electrodes. 

A practical elastic connection between the electrode and the current leads is used 
by Keller with the above-mentioned electrodes (German patent 194897). The suc¬ 
cessive up-and-down movement of the electrodes requires flexible leads between the 
conductor and the carbons. Sometimes an elastic cable of sufficient length serves 
this purpose. This, however, is subject to considerable wear and tear, takes much 

space, and is cumbersome 
for melting furnaces with 
vertical electrodes, espe¬ 
cially so when they lead the 
current in and out, so that 
there is the danger of short 
circuit. 

Keller avoids these diffi¬ 
culties by using thin and 
very flexible leaf springs of 
copper, for example, 0.5 mm. 

! (20 mils) thick, bundled 
into two symmetrically ar¬ 
ranged bundles and held 
together at seveial points by 
rings. Each side of the 
electric holder has a guiding 
rod, which causes the leaf 
springs to be compressed or 
opened in vertical direction 
when the electrodes move 
down and up. The shape 
of the leaves is determined by the distance of the rings, which make knots when the 
springs are deflected or stretched. 

If the lengths of the single-leaf springs are somewhat different from each other, the 
elasticity of each spring is used with best efficiency. There is no danger of a short 
circuit, and the elastic connection is not exposed to the flames of the furnace. This 
construction has given excellent service, and is used in electric furnaces of various 
types and employed for a variety of purposes. 



Q 


C 


F=f 


0 


3 E 


] [ 


;] 


Figure 26.—Holder for a block electrode. 


ELECTRODE DIMENSIONS AND EDECTRODE BUNDLES. 

The best cross-section of electrodes is one of the most important questions for the 
consumer. Above all, it is determined by the current density of the electrode. 
Experience is so far the only guide. A number of important papeis on this subject 
have been published or reviewed in Metallurgical and Chemical Engineering. No 
general formula which would be valid for all cases has yet been found for the calcula¬ 
tion of this section. In general, a good electrical and a poor thermal conductivity of 
the electrode are desirable to reduce the voltage drop and development of heat by the 

































































































































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


61 


1 


u \ 




/ 

/ 

' 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ _ 

/ 

/ 

/ 

±j 


o 


D 


joulean effect, and so prevent any appreciable loss of heat through the electrodes. 
Much systematic work remains to be done to find the best conditions for improving the 
heat balance of furnaces in special cases. In view of the fact that the thermal effi¬ 
ciency of the electric arc furnace is 50 per 
cent or more, these energy losses through the 
electrodes are of minor importance. a 

The current density of electrodes depends 
on the sectional area. It has been proven 
that round electrodes of from 70 to 100 
mm. (2.8 to 4 inches) diameter, as used, 
for instance, in the Stassano furnace, can 
carry 20 to 25 amperes per square centi¬ 
meter (129 to 161 amperes per square 
inch).& 

Larger sections are used in the electric 
steel furnaces of Heroult, Girod, Keller, 
etc. They can not carry any such current 
density. Up to a section of 400 by 400 mm. 

(16 by 16 inches) 5 amperes per square 
centimeter (32 amperes per square inch) 
are allowed with a temporary overload of 6 
to 7.5 amperes per square centimeter (39 to 
48 amperes per square inch). 

The large differences in the current- 
carrying capacity of electrodes of differ¬ 
ent section are partly due to the thermal 
and electrical conditions mentioned above. 

Most of the commercial electrodes are 
made in presses. The capacity of the 
press is limited by its dimensions and de¬ 
sign, and it seems likely that the smaller 
sections of electrodes produced under a 
higher pressure have a denser structure. 

From this it would seem that the current- 
carrying capacity of the electrode is de¬ 
termined by the pressing capacity of the 
machines. 

The area of surface exposed to the cooling 
effect and the resistance of the electrode 
play, no doubt, an important part in these 
considerations. 

It is noteworthy, however, how small the 
differences in the physical constants of small 
and large electrodes really are. For the identical carbon mixture we find the follow¬ 
ing values: 



Figure 27.- 


-Modification of holder for block 
electrode. 


Size of electrode. 

80 mm. (3-J inches) round. 
300 by 300 mm. (Ilf by 
Ilf inches) square. 


Specific resistance. 
48 to 50 ohms. 
65 to 68'ohms. 


Specific gravity. 

1.55. 

1.50 to 1.52. 


a The reviewer of this article states that he differs on this point. The author of this bulletin also differ 
with the statement above made. 

b The reviewer states that graphite electrodes are used in these furnaces, and account for the remarkable 
differences from the figures given immediately after for the electric steel furnaces of Heroult, Girod, 
Keller, etc. 














































































































62 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 



The consumer of electrodes is anxious to reduce the voltage drop by increasing the 
section of the electrode. The size of section is limited by the design of the furnace 
and by the facilities of the electrode manufacturer. Recently much progress has 
been made so that square electrodes of 550 by 550 mm. (21.6 by 21.6 inches) section 
and round ones of 625 mm. (25 inches) diameter can now be bought from the leading 
factories. 

These large sections naturally involve some disadvantages. The current-carrying 
capacity is reduced, the mechanical strength decreases with increasing section, and 

the weight of a single 
electrode reaches a con¬ 
siderable figure. I n case 
of a broken electrode 
very heavy pieces might 
have to be removed 
from a steel bath and an 
entire heat might be lost 
by carburization or by 
cooling off. 

The carbide industry, 
in which large amounts 
of energy had to be 
handled at an early date 
had previously chosen a 
different way to over¬ 
come the above difficul¬ 
ties. Six or eight or 
other numbers of smaller 
electrodes were com¬ 
bined into one package 
or bundle and lowered 
by means of cranes into 
the furnace. The size 
of the individual elec¬ 
trode is often chosen as 
250 by 350 mm. (10 by 
14 inches). The elec¬ 
trodepackages, as illus¬ 
trated in figures 19, 20, 
and 45, leave an unused 
butt. 

The amount of these 
butts is kept at a mini¬ 
mum by the use of 
proper water-cooled 
holders, and whatever 

remains is used in the carbide furnaces for patching the hearth. 

The electric pig-iron furnace in Dommarfvet used three electrodes, each composed 
of two individual carbons; the over-all section was 660 by 330 mm. (26 by 13 inches). 
In Trollhattan ° each electrode consists of four pieces of 2 mm. (0.79 inch) length and 
330 by 330 mm. (13 by 13 inches) section, giving a section of 660 by 660 mm. (26 by 26 
inches) over all. 



Figure 28.—Electrode holder used by the Aktisbolaget Elektrometall 

Ludwika. 


a This practice is no longer followed at Trollhattan, round electrodes being used. 






























































































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 63 

The combining of smaller pieces offers the additional advantage that the individual 
electrode has a higher current-carrying capacity and that considerable losses of energy 
are avoided. 

Attempts have been made to increase the conductivity of the electrode, for the 
sake of decreasing the section, by providing a metallic core. Heroult suggested as 




O 


Vjw-:: 











Figure 30.—Electrode with iron connection in 
top. 




Figure 29.—Electrode holder used by Nathusius. Figure 31.—Screw-bolt electrode connection. 


early as 1892, in United States Patent 473117, to bore holes through the electrodes 
and fill these with aluminum alloys or silicon alloys. 

The Planiawerke in Rutibor, Germany, improve the conductivity and mechanical 
strength by metal fillets introduced before or after the baking of the electrodes. 
(Norwegian Patent 21366, 1910.) The melting or volatilization point of the metal 



































































































64 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


should be below the reaction temperature of the furnace. Measurements show that 
the resistance of such electrodes “reinforced” by a metallic core can be reduced to 
at least one-half of the original with a comparatively small cross section of the core. 

The process is particularly intended for use with rather long continuously fed 
electrodes. Certain alloys can be introduced into the steel by using same as the core. 




Figure 32.—Combination of four screw-bolt 
electrodes. 



,i—i, 






Figure 34.—Electrode connection used by Keller. 


Figure 33. — Electrode connection used by 
Lessing. 


According to Perkins a tube of the carbon or iron can be filled with lime, iron oxide, 
or other slag-forming materials and thus deliver the very liquid refining slag at the 
hottest point of the bath. 

Figure 35 shows the form of electrode holder used in the Stassano 
furnace. 






































































































































DESIGN AND CONSTRUCTION OF ELECTRIC FURNACES. 


65 


JOINING OF ELECTRODES. 

Owing to the fact that the item “cost of electrodes per ton of 
metal produced” or “per pound of metal produced 7 ’ is excessive if 
the electrode is rejected as soon as it becomes too short to permit 
further use, as is the used electrode shown in figure 15, numerous 
methods have been devised for joining electrodes together so as to 
permit continuous feeding. This is generally done in one of three 



ways (fig. 36), namely, (1) by means of a nipple molded with a screw 
thread, and made out of the same material as the electrode; (2) by 
means of a cylindrical threaded plug, which is screwed equal distances 
into the ends of the two electrodes to be joined; or (3) by means of a 
threaded male and female joint. 

Fitzgerald a states that as a result of numerous experiments it 
was found that the joint best suited to the average furnace needs is 

a Fitzgerald, F. A. G., Hinkley, A. T., Experiments with furnace electrodes: Trans. Am. Electro- 
chem. Soc., vol. 23, 1913, p. 333. 
























































































































































































66 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


made by using a threaded plug, in the manner stated second above 
and that a shallow rounded thread proves better than a pointed one 
or even a truncated one, as there is less tendency to breakage during 


assembling. 


ELECTRICAL LOSS AT JOINTS. 


A certain loss of voltage takes place at these joints. u This loss 
has been found to be 2 to 2.5 volts for square electrodes of 280 to 330 
millimeters (11 to 12 inches) side length with a current density of 5 
amperes per square centimeter (32.25 amperes per square inch). This 
would mean a drop of 4 to 5 volts for an electric steel furnace with 
two arcs in series, or a loss of 16 to 20 kilowatts for a 500-kilowatt 
load, which represents 3.5 to 4 per cent of the total energy/” a Such 

being the case, the saving 




p'TI 




in electrode material and 
time by joining electrodes 
together has to be bal¬ 
anced against this loss. 

The reason for this loss 
of voltage at the joints is 
due to the fact that if 
the electrode be joined 
by means of a threaded 
joint, as shown in figure 
36, there is liable to be 
good contact only be¬ 
tween the threaded parts 
(<a and c) of the elec¬ 
trodes, whereas the sur¬ 
faces of the ends of the 
electrodes do not come in contact with each other at all. On this 
account, the current is all crowded on to that part of the electrode 
carrying the male thread a , a condition that not only gives rise to 
the loss above mentioned, but causes the electrode to become so 
overheated at this spot as to cause it to go to pieces. It has been 
suggested that with electrodes of amorphous carbon this difficulty 
might be overcome by joining the electrodes together by a graphite 
dowel, as also shown in figure 36. As the conductivity of graphite 
is about four times that of amorphous carbon, the graphite dowel 
could be made of such a size as to readily carry the full amount of 
current carried by the carbon electrode, and in this way the loss 
above referred to would be reduced to a minimum. 



Figure 36.—Three types of electrode joints. 


a Anon., Die Elektrodenfassungen bei Elektrodfen: Stahl und Eisen: vol. 33, 1913, p. 472. Translated 
by Kennedy, A. E., Met. and Chem. Eng., vol. 11, June, 1913, p. 323. 












































































COST OF ELECTRIC POWER. 67 

In this connection the article a mentioned above may well be 
quoted, as follows: 

It has also been proposed to make these connecting studs from metal. This, how¬ 
ever, would defeat the special purpose of these studs. They would melt and vola¬ 
tilize and not fill their purpose, since their object is to use the last piece of the elec¬ 
trode. This latter aim is completely reached by a joint containing small particles of 
metal embedded in carbon. 

The disadvantages of this method are as follows: 

1. The manufacture of the accurate inner thread and nipples and other shapes 
increases the cost of the electrode construction. 

2. The contact resistance causes losses of energy. 

3. The joint is apt to loosen and to increase these losses or the end of the electrode 
in the furnace may drop off, causing short circuits or other troubles; too tight a joint 
might result in a breaking of the two carbon pieces. (Borchers, Elektrische Oefen, 
2d ed., p. 143.) 

These difficulties are unknown in the use of electrodes wffiich are not joined together; 
it is mainly a matter of calculation whether to join electrodes or not, and the cost of 
power, the cost of electrodes, and their length will decide which of the two methods 
should be used in any case. In cases in which the furnace and the holder allow the 
use of the electrode down to but a small stump it will be in many cases more advisable 
not to join the electrodes. 

The rate at which electrodes are consumed depends largely upon 
(1) whether they are exposed to the action of an oxidizing atmos¬ 
phere, and (2) the nature of the charge, or of the material that is 
being heated in the furnace. 

COST OF ELECTRIC POWER. 

Naturally, all other conditions being favorable, the use of the elec¬ 
tric furnace in the smelting of ore and the production of metals and 
ferro-alloys will depend largely upon the cost of electric power. 

HYDROELECTRIC POWER. 

i 

Ordinarily one thinks of electricity as being most easily developed 
by water power. In a way this is true, but as to whether power can 
be as easily and cheaply produced in this manner as by steam or gas 
will of course depend on the initial cost of installation, which, in 
turn, depends, among other things, upon the following: 

1. The mean average flow of water for 12 months. 

2. Whether expensive reservoirs have to be constructed. 

3. Whether these reservoirs are situated a long distance from the 
site of the power plant, thus necessitating the construction of long 
ditches, flumes, tunnels, or pipe lines. 

4. Whether expensive dams have to be constructed. 

In all the forms of water power that are available, either one or all 
of the above-mentioned prerequisites have to be given serious con- 

a Anon., Die Elektrodenfassungen bei Elektrobfen: Stahl und Eisen: vol. 33,1913, p. 472. Translated 
by Kennedy, A. E., Met. and Chem. Eng., vol. 11,1913, p. 321. 




68 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


sideration, although the cost of installation may be as low as $48 
per kilowatt or as high as $400. As shown in the accompanying 
table (p. 70), the cost of hydroelectric power to the consumer may 
vary from $5 to $60 per kilowatt-year, depending largely on local 
conditions. 

POWER PRODUCED BY GAS ENGINES AND STEAM TURBINES. 

Of late years a great deal has been written regarding the production 
of cheap electric power by generators driven by gas engines. Although 
power can be produced cheaply by such generators when waste gases 
from a blast furnace are utilized, yet if coal be burned in gas pro¬ 
ducers to produce the necessary gas, even though the coal used be of 
inferior quality, and by-products are recovered, the cost of electric 
power made in this way is rather likely to be more than what is gen¬ 
erally supposed to be the cost when gas engines are used for driving 
the generators. 

With the introduction of steam turbines of high efficiency the cost 
of electric power has been much reduced during recent years. From 
the figures in the two tables following, which were kindly supplied to 
the Bureau of Mines by a reliable engineering firm, it seems that with 
large units the cost per kilowatt-hour is less for a turbine-driven 
generator plant than for a gas-engine plant. 

Plants driven by producer gas from bituminous coal and turbine 
plants of 2,000 kilowatts, 4,000 kilowatts, 6,000 kilowatts, 8,000 
kilowatts, and 10,000 kilowatts normal capacity are considered in 
these tables. In each plant all units are of uniform size. The data 
are given on the basis of a 75 per cent load factor. The maximum 
size of the gas engines covered is 2,000 kilowatts; hence corresponding 
data are given for turbines. Power-plant cost includes everything 
from real estate up to complete installation of all auxiliaries. The 
tables follow. 

Cost of installation of steam-turbine and of gas-engine power plants. 0 





Cost per kilowatt of 

Size of 

Size of 

Number 

installing— 

plant. 

units. 

of units. 



Turbine. 

Gas engine. 




Kilowatts. 

Kilowatts. 




2,000 

500 

4 

$82.00 

$133.00 

4,000 

1,000 

4 

71.00 

115.00 

6,000 

2,000 

3 

67. 00 

106.00 

8,000 

2,000 

4 

64.50 

104.00 

10, 000 

2,000 

5 

62.50 

102.50 

10,000 

1 6,000 

\ 2,000 

1 

} 61.00 


z 



a The fixed charges for each type of plant were as follows: Interest, 5 per cent; taxes and insurance 2 Der 
cent; amortization, 3.5 per cent; total, 10.5 per cent. ’ ^ 














COST OF ELECTRIC POWER. 


69 


Operating cost of gas-engine and of steam-turbine power plants. 
COST ITEMS FOR GAS-ENGINE PLANT. a 


1 

Size of 
plant. 

Labor. 

Repairs 

and 

mainte¬ 

nance. 

Oil, waste, 
and 

supplies. 

Fuel.i* 

Total 

operating 

cost. 

Fixed 

charges. 

Total. 

Kilowatts. 

2,000 

4,000 

0.163 

0.044 

0.032 

0.27 

0.509 

0.236 

0. 745 

.145 

.039 

.029 

.27 

.483 

.204 

.687 

6,000 

.130 

.035 

.026 

.27 

.461 

.188 

.649 

8,000 

.124 

.034 

.025 

.27 

.453 

.184 

.637 

10,000 

.123 

.033 

.025 

.27 

.451 

.182 

.633 


COST ITEMS FOR TURBINE PLANT. a 


2,000 

0.106 

0.019 

0.020 

0.41 

0.555 

0.133 

0.688 

4,000 

.088 

.017 

.017 

.36 

.482 

.115 

.597 

6,000 

.072 

.017 

.014 

.338 

.441 

.108 

.549 

8,000 

.067 

.016 

.013 

.332 

.428 

.104 

.532 

c 10,000 

.066 

.016 

.013 

.33 

.425 

.101 

.526 

d 10, 000 

.064 

.0155 

.0125 

.323 

.415 

.099 

.514 


a In cents per kilowatt-hour. 
b At $3 a ton. 

c Consisting of five 2,000-kilowatt units. 

d Consisting of one 6,000-kilowatt unit and two 2,000-kilowatt units. 


In considering items pertaining to the two 10,000-kilowatt turbine 
plants, it should be noticed that the plant with the larger units has 
lower costs for each item. A similar arrangement might be made 
for the other turbine plants, with a decreased cost resulting; for 
example, the plants might be arranged as follows: 

2,000-kilowatt plant in one 1,000-kilowatt unit and two 500-kilo¬ 
watt units. 

4,000-kilowatt plant in one 2,000-kilowatt unit and two 1,000-kilo¬ 
watt units. 

6,000-kilowatt plant in one 3,000-kilowatt, one 2,000-kilowatt, and 
one hOOO-kilowatt unit. 

8,000-kilowatt plant in one 4,000-kilowatt unit and two 2,000-kilo¬ 
watt units. 

If the heating value of the coal is assumed to be 13,000 British 
thermal units per pound for all prices of coal, the only item in the 
operating cost affected by the varying price would be fuel cost. For 
example, in a 4,000-kilowatt turbine plant the effect of varying fuel 
prices might be as indicated below: 


Cost of coal 
per ton. 

$1 . 

2 . 

3 . 

4 . 


Fuel cost per 
kilowatt-hour. 

.$ 0.12 

.24 

.36 

.48 




























70 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


In the table following are given some approximate cost figures 
for hydroelectric power when used for electric furnaces or electro¬ 
chemical purposes, with a high load factor: 

Cost of electric power for electric furnaces or electrochemical purposes with a high-load 

factor . 


Location of plant. 

Power company. 

Nature of power. 

Cost per 
kilowatt- 
year. 

Product at the 
present time. 

Prflintrpp England_. 

Lakes & Elliott Steel 

Gas engine. 

$110 

Steel. 


Foundry. 




Sheffield, "England. 

Municipal Svstem. 

Steam. 

87 

Do. 

La Praz, Savoie, France.. 

Electrometallurgical Co. of 

Hydroelectric. 

16 

Aluminum, steel, 


France. 



carbide. 

Livet, Tsore, France. .. 

Keller, Leleux & Co. 

.do. 

13 

Ferro-alloy. 

Ugine, Savoie, France.... 

Girod Electro metallurgy 

.do. 

18 

Ferro-alloy, steel. 


cal Co. 




Bonn, Germanv 

Municipal System. 

Steam. 

92 

Steel. 

Remsheid, Germany.... 

Lindenber Steel Co. 

.do. 

87 

Do. 

Volklingen, Germany.... 

Rochling Iron & Steel Co.. 

Steam, gas. 

83 

Do. 

Meraker, Nor wav. 

Meraker Electric Smelting 

Hydroelectric. 

8 

Ferro-alloys, car- 


Co. 



bide. 

Notodden, Norway. 

Norwegian Saltpeter Co... 

.do. 

7 

Nitrates. 

Rjukan, Norway. I. 

_do. 

.do. 

5 

Do. 

Tyssedal, Hardanger,Nor- 

Tyssedal Power Co. 

.do. 

10 

Carbide, cyanam- 

way. 




ide. 

Trollhattan, Sweden. 

Royal Power Plant. 

.do. 

9 to 12 

Iron, zinc, ferro- 





alloy, paper. 

South Verron, Vt. 

Connecticut River Power 

Water and steam.. 

53 

General. 

Shelburne Falls, Mass_ 

to. 

.do. 

Water (secondary) 

29 

Do. 

Turners Falls, Mass. 

Turner Falls Power Co.... 

Water and steam . 

60 

Do. 

Do. 

.do. 

Water (secondary) 

26 

Do. 

Rumford Falls, Me. 

Rumford Falls Power Co.. 

Hydroelectric....’. 

26 

Paper. 

Niagara Falls, tj. S. 


.... .do. 

26 

Electrochemical. 

Niagara Falls’ Canada.... 


.do. 

20 

Do. 

South Carolina. 

Southern Power Co. 

.do. 

25 

N itrates. 

South Chicago, Ill. 

Illinois Steel Co. 

Steam, gas. 

43 

Steel. 

South Carolina. 

Southern Aluminum Co... 

Hydroelectric. 

25 

Aluminum. 

Snake River, Idaho. 

Southern Idaho Power Co. 

.do. 

12 

General. 

Heroult, Cal.. 

Northern California Power 

.do. 

16 

Pig iron. 


Co. 




OPERATING CONDITIONS OF ELECTRIC FURNACES. 

In the operation of an electric furnace one or more of the following 
conditions may be encountered: 

A high enough temperature may not be reached in consequence 
of one of the following conditions: 

1. The furnace may be “ underpowered/’ that is, may not have 
enough electric current supplied to it, and this in turn may be due 
to lack of either power-line supply, transformer capacity, or insuf¬ 
ficient voltage. 

2. The material to be treated may be fed too rapidly. 

3. The radiation losses may be too great. 

Then, too, the temperature may be too high. With furnaces 
using voltage control this fault may be remedied b} T cutting down 
the voltage of the current used, but if a constant voltage be used and 
the temperature is too high about the only remedy is to feed in 
more charge. If this procedure will remedy the defect it indicates 
that the furnace has a capacity greater than that which has been 









































































OPERATING CONDITIONS OF ELECTRIC FURNACES. 71 

calculated for it. However, an “overpowered” furnace is generally 
short lived, as the walls are unable to conduct the heat away fast 
enough to prevent their destruction through fusion. Then, too, as 
is self-evident, the higher the temperature the greater will be the 
heat losses through the furnace walls and through the electrodes. 
Hence, if there is no advantage to be gained from a temperature 
higher than is needed for the necessary reactions of the process, it can 
be said that if in operating an electric furnace an excessive temperature 
is obtained an error has been made in calculating the size of the fur¬ 
nace or in the amount of energy needed. However, as is also self- 
evident if the excess heat can be absorbed by a faster feeding of the 
material to be smelted the heat losses per pound of material smelted 
w r ill be less, for the heat losses through the electrodes and walls are 
continuous, and hence are less per pound of material smelted if 20 
pounds be treated per minute than if only 10 pounds be treated. 

CONCLUSION. 

In conclusion the authors repeat that their object has been not to 
present a technical discussion of the electric furnace, but to acquaint 
the layman, so to speak, with some of the most important essentials 
in connection with the use and construction of the electric furnace 
as used in metallurgical work and to assist those who are unfamiliar 
with the subject to a better understanding of the processes described 
in parts II and III of this bulletin and in Bulletin 67 on “Electric 
Furnaces for Making Iron and Steel.” 

44713°—Bull. 77—16-6 


PART II. THE SMELTING OF METALS IN THE ELECTRIC 

FURNACE. 


By Dorsey A. Lyon and Robert M. Keeney. 


INTRODUCTION. 

The object of Part II of this bulletin is to present briefly a state¬ 
ment of the extent to which the electric furnace has been applied 
to the metallurgy of metals when the product is in the form of the 
metal and not of a ferro-alloy. For example, the metals copper and 
zinc are discussed in this part and the ferro-alloys, such as ferrochrome 
and ferrotungsten, are discussed in Part III. No attempt is made to 
present exhaustively the details of each particular process, as persons 
desiring such information can obtain it from the references given. 

Under this part there is discussed the electric smelting of the ores 
of aluminum, copper, gold and silver, iron, lead, complex sulphides, 
and zinc. The subject of iron has been treated briefly, as compared 
with its importance, because it has already been discussed fully in 
Bulletin 67.° 

ALUMINUM. 

INTRODUCTION. 

In the manufacture of aluminum the electric furnace has a field 
entirely its own, for there is no process by which alumina is reduced 
to aluminum in a combustion furnace. In the metallurgy of alumi¬ 
num, as stated in Part I of this bulletin, the electric current not only 
supplies the necessary heat, but also reduces the metal from the ore. 
The first application of electrolysis to the reduction of aluminum 
was in 1864 when Bunsen and Deville, each working independently, 
obtained the metal by the electrolysis of fused aluminum chloride. 6 
Previous to the introduction of the present method the aluminum 
was obtained chiefly through the reduction of the halide salts of the 
metal with metallic sodium. 

In 1884 the Cowles process was patented, in which alumina 
was reduced with carbon in the presence of copper in an electric fur¬ 
nace of the resistance type. An alloy 0 of aluminum and copper was 

a Lyon, D. A., and Keeney, R. M., Electric furnaces for making iron and steel: Bull. G7, Bureau of Mines, 
1913,142 pp.,36 figs. 

b Thompson, M. D., Applied electrochemistry, 1911, p. 228. 

c U. S. patent 319795. 

72 






ALUMINUM. 


73 


the product. It was known then that alumina could be reduced to 
aluminum as a result of being heated with carbon to a temperature 
higher than 2,100° C., but all of the aluminum formed w r as mixed 
with aluminum carbide, from which it was removed by a re fin ing 
process. In the Cowles process the copper v^as used to prevent the 
formation of aluminum carbide, but of course the process had the 
objection that the aluminum was not obtained as pure metal but as 
an alloy. 

In 1886 Hall 3 found that alumina dissolved in a molten mixture 
of aluminum fluoride and the fluoride of another metal formed an 
electrolyte which could be decomposed by the electric current accord- 
ding to the reaction Al 2 0 3 = 2Al + 30. About the same time that 
Hall made his discovery, Ileroult in France made a similar independ¬ 
ent discovery. 

PREREQUISITES FOR THE PRODUCTION OF ALUMINUM BY 

PRESENT METHODS. 

Although aluminum is one of the most abundant of the elements 
that make up the earth’s crust, nevertheless those of its ores that 
are suited to the process of aluminum manufacture, as carried on at 
present, are comparatively scarce. About the only one now used for 
this purpose is bauxite. The great bulk of that produced in the 
United States is mined in Arkansas and Tennessee. Phalen 6 states 
that some bauxite is now mined in central Georgia. 

PROCESSES FOR PURIFYING BAUXITE. 

As all the impurities in the alumina pass into the metal produced, 
it is necessary in both the Hall and the Heroult processes to use 
alumina as pure as possible. This is why the Bayer process found 
considerable application both here and abroad for the purification 
of bauxite. In this process the bauxite is fused with the carbonate 
or sulphate of sodium and the fused mass is washed with water; then 
the sodium aluminate obtained in solution is decomposed by adding 
aluminum hydrate and constantly stirring. Richards c states that 
the decomposition of the solution goes on until the quantity of 
alumina remaining in solution is to the sodium protoxide as 1 to 6. 
This precipitation takes place in the cold, and the pulverent alumi¬ 
num hydrate separated out is easily soluble in acids. The alkaline 
solution remaining is concentrated by evaporation, taken up by 
ground bauxite, dried, calcined, melted, and thus goes through the 
process again. 


all. S. patents 400664 and 400666. 

J> Phalen, W. C. 5 Bauxite and aluminum: Mineral Resources U. S. for 1911, U. S. Geol. Survey, 1912, p. 928. 
cRichards, J. W., Aluminum, its properties, metallurgy, and alloys, 3d ed., 1896, p. 144. 



74 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

Hall also invented and patented at least two processes for this 
purpose, including the lime process of wet chemical treatment (U. S. 
patent 663167, Dec. 4, 1900), which was installed at East St. Louis, 
and a process whereby the bauxite is mixed with a small percentage 
of carbon and calcined, and after calcination is again mixed with 
about 8 to 10 per cent of carbon, some ferric oxide, possibly some 
sort of a flux being added. The impurities such as iron and silicon 
are reduced, and form ferrosilicon of impure grade, which sinks 
to the bottom of the electric furnace, leaving the purified alumina 
at the top. After the alumina has cooled, it is separated from the 
ferrosilicon by electromagnetic methods if necessary. In the patent 
specification, it is stated that aluminum powder is also added, but 
this is not now thought necessary. In England, the British Alumi¬ 
num Co. (Ltd.) purify bauxite by dissolving it in caustic soda and 
then precipitating the alumina by the addition of some previously 
precipitated alumina. 0 

HALL PROCESS FOR PRODUCING ALUMINUM. 

Although more than 20,000 tons of aluminum is produced each year 
in the electric furnace, little published information is available con¬ 
cerning the methods of manufacture, as all manufacturers try to 
keep their processes secret. In this country practically all of the 
aluminum produced is obtained by the use of the Hall process. The 
essential facts regarding this process are as follows: The ore (bauxite) 
is first purified by being treated either by the lime process or the 
electric-furnace process. It is then charged into an electric furnace 
containing a bath of cryolite or a mixture of aluminum fluoride with 
the fluoride of another metal, the bath being kept molten by the heat 
generated by the passage of the electric current. The alumina is 
thus decomposed into aluminum and oxygen by the electrolyzing 
action of the direct current. A concise description of the process 
used in practice is given by Neumann and Olsen 6 from whose article 
the following information is quoted: 

A photograph of an aluminum cell has been published only once, so far as is known, 
by J. W. Richards;c the cell shown is evidently a cell of Charles M. Hall, as used 
some years ago. The illustration shows 20 round anodes in two parallel rows in a high 
iron box. Quite detailed notes illustrated by sectional diagrams were also given 
later by Winteler.^ The cells described by Winteler are also rectangular, and are 
also provided with a double row of carbon electrodes. More recently, circular cells 
have been introduced, the anodes being distributed over the whole surface. 

a Cachu, William, London Elec. Rev., 1911, vol. 68, p. 99. 

b Neumann, B., and Olsen, H., Production of aluminum as a laboratory experiment: Met. and Chem. 
Eng., vol. 7,1910, p. 185. 

c Electrochemical Industry, vol. 1, 1903,p. 160. 

d Winteler, Aluminium Industrie, 1903. 




ALUMINUM. 75 

HEROULT PROCESS FOR THE MANUFACTURE OF ALUMINUM. 

In principle, the Heroult process is the same as the Hall process, 
the reported differences being in the composition of the electrolyte 
and possibly in the shape of the furnace. In fact, the two processes 
are so similar that when the discovery of the reaction was made simul¬ 
taneously, there was no patent litigation, but the Hall Company took 
the American field and the Heroult people the European, a condition 
that was maintained until recently, when the last of the Hall and 
allied patents expired in the United States. Now the Heroult in¬ 
terests are erecting a plant in North Carolina. 

In Europe at the present time the manufacture of aluminum is 
conducted exclusively in furnaces (see fig. 37) having a carbon 
block as the cathode, 
forming the bottom of 
the furnace, upon which 
the molten aluminum 
collects, and several 
upper carbon anodes, 
while the bath is kept 
molten entirely by the 
heat generated due to 
the passage of the elec¬ 
tric current. The cross 
section is in all cases 
rectangular. The fur¬ 
naces seen recently by 
one of the writers at a 
French aluminum plant 
were rectangular and of 

the general shape of the 
Heroult Steel furnace, FlamE ST.-Almntoum furnace,^, shell; 6, lining; o, anodes; 

but not so large. They 

were about 5 feet long, 3 feet wide, and 3 feet deep externally. 
Each furnace rested on the floor of the building without special 
foundations, so that furnaces could be picked up and moved around 
readily with a crane. There were eight carbon anodes projecting 
into the bath and connected to the positive side of the circuit, while 
the electrodes in the carbon bottom are connected to the negative 
side of the circuit. There is an electrode in the bottom correspond¬ 
ing to each of the anodes. In this case the bottom is only partially 
covered by the molten aluminum. 

A second type of furnace has a bottom composed of a mixture of 
tar and ground coke or electrode waste, which is rammed in around 
four large iron plates connected to the negative side of the circuit. 
There are four rows of anodes containing six to eight electrodes per 
































































76 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


row. In both types of furnace the bottom is inclined toward the 
tap hole, and each electrode is arranged so that it can be regulated 
independently of the others. 

In the Heroult as in the Hall process the composition of the bath 
is kept secret, but in both processes the specific gravity of the bath 
must be less than that of the metal, so that the latter can collect on 
the bottom. Cryolite melts at 1,000° C., but its melting point is 
reduced to 915° C. by the addition of 5 per cent alumina. By the 
use of calcium fluoride the melting point of cryolite can be further 
reduced to 800° C. Cryolite has a specific gravity of 2.92 when 
solid and 2.08 when liquid, whereas aluminum has a specific gravity 
of 2.6 when solid and 2.54 when liquid. It is not considered advis¬ 
able to have more than 25 per cent of aluminum, in the form of 
alumina, in the molten bath. Although aluminum fluoride can also 
be used for lowering the melting point, the most common flux is 
calcium fluoride. 

Theoretically, 42 grams (0.092 pound) of aluminum per kilowatt- 
hour should be produced by the electrolysis of alumina in a bath of 
cryolite. Practically, the foreign manufacturers using the Heroult 
process make 30 grams (0.066 pound) of aluminum per kilowatt- 
hour, which gives an efficiency of 71 per cent. 

The furnaces take about 75 kilowatts each and produce from 50 
kilograms (110 pounds) to 55 kilograms (121 pounds) per 24 hours. 
The voltage used is from 8 to 10 volts and the density of current 
from 1.5 to 3 amperes per square centimeter. The consumption of 
alumina per pound of finished aluminum is theoretically 1.888 
pounds and practically 2 pounds. For each pound of aluminum pro¬ 
duced tjiere is a consumption of 0.1 pound of cryolite and 0.9 pound 
of carbon anodes. 

The main progress in aluminum manufacture, as far as can be 
determined, has been in the purification of the bauxite into alumina 
before it is charged into the electrolytic cell, mention of which has 
already been made. 

SERPEK PROCESS. 

A new process, the Serpek, has been devised and is being introduced 
in Europe. In this process bauxite is heated to a temperature suffi¬ 
cient to cause the formation of aluminum nitride, which is decom¬ 
posed by the action of water into alumina and ammonia, according to 
the reaction 2 AIN + 3H 2 0 = A1 2 0 3 + 2NH 3 . For the preliminary reac¬ 
tion an electric furnace is not absolutely necessary, as producer gas can 
be used as a fuel, but of course an electric furnace is used to reduce the 
refined alumina to metallic aluminum. The process thus provides a 
method for the fixation of nitrogen and for the purification of bauxite 
to produce pure alumina for the electrolytic cell. 


ALUMINUM. 


77 


The raw bauxite is first calcined by being passed through a revolv- 
ing cylindrical kiln similar to a cement kiln. The calcined bauxite 
passes by gravity to another similar kiln, before entering which it is 
mixed with carbon and then treated with nitrogen. Halfway down 
the lower kiln is a detachable electric resistance furnace which is 
intended to raise the temperature to 1,800° to 1,900° C. The mate¬ 
rial is discharged from the lower end of this kiln into an air-tight 
receiver. Producer gas, consisting of one-third carbon monoxide 
and two-thirds nitrogen, is introduced at the lower end of the lower 
kiln. This gas enters at a temperature of 400° C., but when it reaches 
the electrically heated part of the furnace and attains a temperature 
of 1,800° C., it reacts upon the charge to form aluminum nitride. 

PRESENT STATUS OF ALUMINUM MANUFACTURE IN THE UNITED 

STATES. 

The following table,® showing the production of aluminum since the 
beginning of the industry in 1883, and the consumption of the metal 
since 1904, gives an idea of the magnitude of the industry in this 
country: 

Production of aluminum in the United States, 1883-1904. 


Year. 

Pounds. 

Year. 

Pounds. 

1883 . 


83 

1899 . 

. 6, 500, 000 

1884 . 


150 

1900 . 

. 7,150,000 

1885 . 


283 

1901 . 

. 7, 150, 000 

1886 . 

3,000 

1902 . 

. 7, 300, 000 

1887 . 


18, 000 

1903 . 

. 7, 500, 000 

1888 . 


19, 000 

1904. 

. b 8, 600, 000 

1889 . 


47,468 

1905 . 

. Ml, 347, 000 

1890 . 


61,281 

1906 . 

.6 14, 910,000 

1891 . 


% 0 , 000 

1907 . 

. b 17,211,000 

1892 . 


259,885 

1908 .. 

. 6 11,152, 000 

1893 . 


333,629 

1909 . 

. b 34, 210, 000 

1894 . 


550,000 

1910 . 

. b 47,734,000 

1895 . 

1896 . 

. h 

920,000 
300, 000 

1911 . 

.& 46,125,000 

1897 . 

1898 . 

. 5 

000, 000 
200, 000 

Total . 

. 239,751,779 


Until recently there was only one company producing aluminum 
in the United States, and that company controlled the Hall patents. 
Now that these patents have expired, as before stated, French inter¬ 
ests are erecting a plant at Whitney on the Yadkin River in North 
Carolina. Work is being pushed rapidly on this plant, which is to be 

capable of producing 5,000 tons annually. 

In 1907, the company controlling the Hall patents had a total plant 
capacity of about 57,000 kilowatts, of which 45,000 was in the United 

a Phalen, W. C., Bauxite and aluminum: Mineral Resources U. S. for 1911, U. S. Geol. Survey, 1912, 
p. 932. 

b Consumption. 








































78 


the Electric furnace in metallurgical work. 


States and 12,000 in Canada. The company failed to get permission 
from Congress to increase some of its water-power developments and 
at present about 4,000,000 pounds of aluminum is annually imported 
into the United States, as this company alone can not supply the 
domestic demand. It is, however, building a plant in Tennessee that 
will increase its productive capacity considerably. The demand for 
aluminum has increased rapidly during the past few years, and as 
there are no longer any patent restrictions, it is probable that other 
companies will begin manufacture in the United States. 

FACTORS GOVERNING GROWTH OF ALUMINUM INDUSTRY. 

As can be readily seen from what has already been stated on this 
subject, the growth of the aluminum industry will depend, among 
other things, upon the discovery of new ores of aluminum; that is, 
ores that can be used in the production of aluminum by the processes 
now employed for that purpose, or upon the development of processes 
for the treatment of ores that are not now suited to the Heroult or 
Hall processes, or to processes similar to them. 

NEW SOURCES OF ALUMINA. 

As before stated, bauxite is practically the only ore now used for the 
production of aluminum. However, Phalen a states that experi¬ 
ments with alunite, deposits of which occur near Marysvale, Utah, 
and in Colorado, California, Arizona, and Nevada, indicate that it 
may at some future time become an important source of alumina. 

The mineral alunite is a hydrous sulphate of aluminum and potas¬ 
sium, having the formula K 2 0.3A1 2 0 3 .4S0 3 .6H 2 0, and according to 
laboratory experiments made by SchaUer of the Geological Survey 
contains, when ignited, 32.7 per cent of available potassium sulphate, 
which can be extracted by simple water leaching and evaporation, 
thus leaving a residue of 67.3 per cent, which consists of nearly pure 
aluminum oxide. Such being the case, it would at first thought seem 
as if this ore would be valuable both for its potash content and for 
the aluminum that it contains. As a matter of fact, as pointed out 
in the report of the Geological Survey, the mineral has attracted 
attention as a possible source of potash. However, as Phalen states, 
present known deposits are so far from Eastern markets that alunite 
ores may not be able to compete with Eastern bauxite ores. But as 
bauxite contains a considerable proportion of iron oxide, silica, and 
titanium oxide, and requires purifying before being reduced to 
metallic aluminum, whereas the residue remaining after the leaching 
of ignited alunite consists of practically pure aluminum oxide, it 
would seem that this advantage, together with the fact that the 


a Phalen, W. C., Bauxite and aluminum: Mineral Resources U. S. for 1911, U. S. Geol. Survey, 1912, 
pp. 424-426. 



ALUMINUM. 


79 


available potassium sulphate that alunite contains is a valuable by¬ 
product, would more than offset added transportation charges to 
Eastern markets. 

PROCESSES FOR PRODUCING ALUMINUM FROM ORES OTHER 

THAN OXIDES. 

Patents covering the production of aluminum from molten elec¬ 
trolytes seem to cover every possible method of obtaining aluminum 
from its ores,® so that one would think that little more could be done 
along this line; but, as in other branches of metallurgical work, new 
ideas are being constantly advanced and patents are obtained on 
new and generally untried inventions until they seem to be without 
end. 

As previously stated, bauxite, which is practically the only ore 
used for the production of aluminum, is found in comparatively few 
places. Moreover, it not only has to be transported long distances, 
but also requires a costly preliminary treatment for the purpose of 
freeing it as far as possible from all constituents other than alumina. 
Aluminum silicates, on the other hand, can be had almost anywhere, 
and it would therefore seem that the logical thing to do, as regards 
discovering new sources from which aluminum can be obtained, 
would be to perfect commercially feasible processes for the production 
of the metal from those aluminum minerals that are so common. 
Considerable experimental work of this sort has already been done 
and several patents have been granted on processes for extracting 
aluminum from ores containing it in some form other than the oxide. 

tone's method. 

The method proposed by Tone 6 consists of two steps. In the first 
step the aluminum-bearing ore is mixed with the proper quantity of 
carbon, and the aluminum is reduced to aluminum carbide. The 
aluminum carbide is then mixed with some other ore—silica, for ex¬ 
ample. The aluminum carbide and the silica are to be in the pro¬ 
portions expressed by the equation 2 A1 4 C 3 + 3Si0 2 = 8A1.3Si + 6CO., 
and the mixture is fused in an electric furnace yielding, as shown by 
the above equation, a silicon-aluminum alloy. 

If metallic aluminum be desired, the aluminum carbide is mixed 
with aluminum oxide in the proportion expressed by the chemical 
equation A1 4 C 3 + Al 2 0 3 = 6Al + 3C0. As has been shown by Hutton 
and Petavel, c although the oxide of aluminum (alumina) can be 

a See digest of patents taken out prior to July, 1902, in Electrochemical Industry, vol. 2,1904, pp. 165,.. 
166, 210. 

b U. S. Patent 961913, June 21, 1910. 

c Hutton, R. S., and Petavel, J. E. On the direct reduction of alumina by carbon: Electrochem. and 
Met. Ind., vol. 6, 1908, p. 104. 






80 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

readily reduced to the metal by carbon ; yet the temperature at which 
the reduction takes place is sufficiently high to volatilize the metal. 
For this reason, if for no other (as, for example, the reduction of other 
elements contained in the ore, which would alloy with the aluminum), 
Tone claims that it is better to divide the process into two parts, thus 
entailing little or no volatilization loss, and that the production of 
carbides with the electric furnace is highly efficient. However, as 
will be noted, the use of aluminum oxide is an essential part of the 
process where the production of metallic aluminum is desired. 

Tone has also taken out two other patents on the production of 
aluminum from silicates. In one of these (No. 906,338) kaolin is 
mixed with carbon for the purpose of reducing the silica but not the 
alumina. The mixture is fused in an electric furnace, the products 
being alumina and silicon as shown by the following equation: 

Al 2 0 3 +Si0 2 +4C=Al 2 0 3 +2Si+4C0 

The alumina after separation from the silicon can be used for the pro¬ 
duction of aluminum by the usual methods. Tone states that the 
reaction shown above may be facilitated by adding base metals or 
ore to the charge, as the base metal alloys with the silicon and so 
brings about a more complete reduction of the silicon. For example, 
if 222 parts of calcined kaolin be mixed with 48 parts of carbon and 
56 parts of iron, then the reaction in the electric furnace is shown by 
the following equation: 

Al 2 0 3 .2Si0 2 +4C+Fe=Al 2 0 3 +FeSi 2 +4C0 

After the fused product has been tapped from the furnace, the sili- 
eide is separated from the alumina, after which the alumina may be 
treated for the production of aluminum in the usual manner. 

Alf-Sinding Larsen has also taken out a patent (U. S. No. 927758) 
that closely resembles that of Tone. In his process he proposes to 
fuse silicates of aluminum in an electric furnace in contact with iron 
(scrap iron or iron ore) and coke. The product of the fusion is ferro- 
silicon and alumina. The alumina can then be treated in the usual 
manner for the production of aluminum. 

BETTSES PROCESS. 

Briefly stated, the process proposed by Betts consists of the follow¬ 
ing steps: 

1. Iron ore and aluminum ore such as bauxite or kaolin are charged 
with fuel into a blast furnace, similar to an iron blast furnace, but 
operated at a higher temperature than the latter. The product is 
iron-aluminum-silicon. 

2. As aluminum is the most readily oxidized, sulphurized, or chlo- 
ridized metal of the iron-aluminum-silicon compound, aluminum may 


IRON. 


81 


be extracted by means of either oxidizing, sulphurizing, or chloridiz- 
ing agents. For example, by treating the iron-aluminum-silicon 
metal with silica at a high temperature, the aluminum of the metal 
would be oxidized by the oxygen of the silica, and there would be 
formed pure aluminum oxide and ferrosilicon, provided the iron ore 
is free from lime and magnesia. 

3. Betts claims that aluminum sulphide can be more readily and 
cheaply reduced to aluminum than can the oxide (alumina), and so 
instead of reducing the alumina to metallic aluminum, as is done in 
the Hall and Heroult processes, he proposes to treat it with iron 
sulphide, thus forming aluminum sulphide. This part of the process 
however, is carried out in two steps. The alloy is first treated with 
an insufficient quantity of iron sulphide to react with the aluminum 
present, resulting in practically pure aluminum sulphide. This 
aluminum sulphide is then reduced by electrolysis to aluminum and 
sulphur. 

As the alloy remaining after the treatment in the second step by 
fusion with silica still contains considerable aluminum, it is further 
treated with an excess of iron sulphide. The result of this treatment 
is a matte, which is then used alone or with additional fresh iron 
sulphide in the next treatment of the aluminum alloy. 

IRON. 

PRESENT STATUS OF ELECTRIC FURNACE IN SMELTING IRON 

ORES. 

USE OF COKE AND CHARCOAL. 

As is well known, of the coke charged into an iron blast furnace, 
only about two-thirds is used for producing the heat necessary for 
carrying on the process, the other one-third being used as a reducing 
agent. Therefore, if the electric furnace is used for the smelting of iron 
ores, only enough carbon has to be supplied to unite with the oxygen 
of the ore, or in other words, to reduce it, and for this reason the 
smelting of iron ores in the electric furnace is of much importance 
to the Western Coast States, for there are found iron-ore deposits 
comparatively large, but not suitable blast-furnace coking coals, and 
so the cost of coke makes ordinary blast-furnace smelting too expen¬ 
sive. However, it is, of course, necessary to supply carbon in some 
form as a reducing agent, and even though only one-third as much 
carbon is required for this purpose as is required in ordinary blast¬ 
furnace practice, it may be impossible to obtain even this amount 
at such a cost as will permit the use of the electric furnace. So far 
only coke and charcoal have been tried to any extent as reducing 
agents in the reduction of iron ores in the electric furnace, and for a 
time it was thought that coke could not be successfully used, as sev- 


82 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

eral trial runs at TroUhattan on coke were not successful and later 
the plant at ITarclanger, Norway, where coke was used as a reducing 
agent, after being in operation for about nine months, was forced to 
close down, owing to the fact that with coke the quantity of pig iron 
that could be produced per kilowatt-year of electrical energy expended 
was not nearly as great as can be produced when charcoal is used. 
It was stated that the reason for this was that coke, especially hot 
coke, is a much better conductor of electricity than is charcoal. For 
this reason when coke is used the resistance of the charge becomes 
lowered, and as the smelting in the electric iron reduction furnace is 
done by the heat produced by the resistance encountered by the elec¬ 
tric current in passing through the charge between the electrodes, 
more electrical energy is required to produce the same amount of heat. 
However, Profs, ll. L. Vogt and P. Farup,® of the Norwegian electro¬ 
metallurgical commission, reporting on the causes of the economic 
failure of this plant do not attribute the same to the use of coke, but 
“ partly to the nature of the ores treated and partly to their low iron 
content, conjointly with the unsatisfactory condition of the agglom¬ 
erating roasting oven, and several parts of the electrical equipment.” 
They state that an “excellent quality of pig iron can be produced” 
with coke, and that “the consumption of carbon is the same whether 
charcoal or eoke is employed;” also that the consumption of electrical 
energy was that originally computed by them for both poor and 
rich ores. 

On the other hand, Engineer Gustaf Oedquist, in a statement made 
before the Christiania Polyteknik Forening, says: 

The committee is of the opinion that the type of smelter used did not conduce to the 
unfavorable results at Hardanger. I am of a different opinion. The reason why it is 
not adapted to coke consists in the greater variation in the electrical resistance in the 
furnace itself by the use of coke, owing to which the average load as well as the pro¬ 
duction is diminished. To which must be added that the larger quantity of limestone 
thereby necessitated contributes to a lesser production of pig iron per horsepower-year. 

Considerable experimenting has also been done with coke as a 
reducing agent by the Noble Electric Steel Co. at Heroult, Cal. In 
his summary of deductions Mr. Crawford, the plant manager, states: * 6 

1. Any ordinary grade of coke, by crushing it, can be used satisfactorily from both 
a metallurgical and an electrical standpoint to produce any normal grade of pig iron. 
But, depending on its porosity and crushing strength and its analysis, there is for each 
variety a size to be determined by experiment which will give from all standpoints 
best operating conditions. 

2. Soft, porous cokes are to be preferred over hard, dense cokes, because the former 
can be fed in larger pieces and still insure homogeneity of mixture when the burden 
descends to the smelting zone. Further, they cost less to crush, and there is less loss 
in fines and flue dust because of the larger size which can be used. For ore crushed 

a Anon., Electrothermic iron-ore smelting in Norway: Eng. and Min. Jour., vol. 98, July 25,1914, p. 158. 

6 Crawford, John, Discussion of paper by Robert M. Keeney on “Pig steel from ore in the electric fur¬ 
nace.”: Bull. Am. Inst. Min. Eng., June, 1914, p. 1289. 





IRON. 


83 


to pass a 2£-inch grizzly, a soft, porous coke gives best results when crushed to pass a 
1^-inch grizzly. Certain hard, dense cokes had to be crushed to pass a £-inch grizzly. 

3. If the coke is of the proper size when it reaches the smelting zone, operations may 
be carried on with as high voltage, low current densities, good power factor, and as cool 
a roof when using coke as when using charcoal. 

4. The power consumption per unit of production is higher with coke as a reducing 
agent than with charcoal, but the increase is due to the extra amount of slag made. 
This depends on the composition and amount of ash in the coke and the amount of 
sulphur in the coke. 

5. The carbon consumption per unit of production is higher with coke than with 
charcoal. This is due partly to the greater flue-dust losses from crushed coke than 
from lump charcoal, and partly to the formation of carbides, in the high-lime, desul¬ 
phurizing slag, all of which are not subsequently decomposed. 

6. If electrodes are regulated to form a free-burning arc, the use of coke has no bear¬ 
ing on the electrode consumption. If, however, electrodes are inserted in the charge 
to form a submerged arc, as is our practice, the consumption of electrode material is 
considerably greater, especially with graphite electrodes. This is due principally to 
the greater abrasive action of coke than charcoal, though partly also to the attack of 
the lime slags on the electrode material. We found the electrode loss from breakage 
(using 12-inch graphite electrodes) very excessive, doubtless due in part to the greater 
density of the burden when using crushed coke as against lump charcoal. On this 
account, after carrying our experiments far enough to demonstrate the commercial 
feasibility of operating on coke, we have shut our furnaces down pending alterations 
to permit the use of 24-inch carbon electrodes, which, besides being stronger, will 
better resist the abrasive action of the burden. 

7. With a coke running 1.25 per cent sulphur we had little difficulty in keeping 
the sulphur in the pig below 0.05 per cent, and much of the iron made was under 
0.03 per cent sulphur. 

8. No trouble was found in making foundry irons up to 3.50 per cent silicon or 
higher if desired. In fact, on account of its high, easily reduced, siliceous ash, coke 
will reduce a high-silicon iron somewhat more readily than charcoal. 

9. Except for a somewhat more open grain, no difference has been noted thus far in 
the physical characteristics of iron made with coke and iron made with charcoal. 

10. Crushed coke, especially when high in ash and with a large percentage of fines 
present, has a tendency to cause the burden to hang. This we believe would pro¬ 
hibit its use successfully in a furnace of the shaft type. However, in the rectangular 
furnaces there is an opportunity to dislodge scaffolds by barring down, if the hang 
is of any duration. There are several ways in which the presence of a hang-up can 
be detected before it has become serious. A mixture of 15 to 25 per cent of lump 
■charcoal with the coke is quite effective in keeping the burden from hanging up. 

In conclusion, we may say that coke has nothing to recommend it over charcoal for 
an electric-furnace reducing material, excepting the difference in price. However, 
“black-butts,” screenings, and even breeze if the dust is removed, can be mixed to 
make a satisfactory reducing material. As such grades of coke can usually be secured 
at a very attractive price, this may more than offset the disadvantages of its use. 

The writer apologizes for offering the above statements as “glittering generalities” 
unsubstantiated by definite figures, but, since the data obtained varied considerably 
with the chemical and physical properties of each coke tried and the size to which it was 
crushed, even a synopsis of this rather voluminous data is considered beyond the scope 
of this discussion. 

Inasmuch as charcoal and coke are the only practical reducing 
agents known at present for use on a large scale, and as it would seem 
from what has just been stated that it is impractical to use coke in a 


84 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


furnace of the shaft type, the electric iron reduction shaft furnace is 
necessarily limited to the use of charcoal. Hence it is necessary that 
such a furnace he located in close proximity to a well-timbered region, 
where charcoal as well as electric power can be produced at a low cost. 

POSSIBLE USE OF CRUDE OIL AS A REDUCING AGENT. 

In southern California and in other Western States there are 
rather large iron deposits of high-grade ore but coke is too expensive 
to permit ordinary blast-furnace smelting and the use of charcoal 
for electric-furnace work is entirely out of the question, as there are no 
forests to furnish the wood necessary for its production. On the 
other hand, crude oil is generally rather plentiful and comparatively 
cheap in such districts, especially in California. 

Aside from the possible use of oil in connection with electric-furnace 
work, those interested in the subject have for years been considering 
the possibility of using crude oil as a reducing agent. So far as the 
authors know, the oil has not as yet been so used successfully. That 
the carbon and the hydrogen of the oil will reduce iron oxides is 
self-evident, but as yet no one seems to have been able to solve the 
problem of bringing the ore and the oil together at the proper tem¬ 
perature. As a result of a preliminary investigation conducted by 
the Bureau of Mines as to the possibility of using crude oil as a reduc¬ 
ing agent, it seems as if about the only manner in which crude oil 
may be used for this purpose is first to convert it into a fixed gas and 
then to introduce this into the crucible of an electric furnace, thus 
preheating the gas to such a temperature that it will effectively 
reduce the iron oxides as it passes up through the shaft of the furnace. 
Be that as it may, it is to be sincerely hoped that ultimately a suitable 
process may be devised whereby oil may be used as a reducing agent, 
and thus broaden the field for the possible application of the electric 
furnace in the reduction of iron ores. 

USE OF ELECTRIC IRON REDUCTION FURNACE AT PRESENT. 

That the electric furnace has been successful in the smelting of 
iron ores in districts where the conditions are favorable is shown by 
the fact that 10 furnaces of the Swedish type with a total capacity 
of about 22,000 kilowatts have been erected in Sweden, Norway, and 
Switzerland. In this country there is one iron plant of two electric 
furnaces with a total capacity of 5,000 kilowatts in operation at 
Ileroult, Cal. The type of furnace used in California is different from 
that used in Sweden, owing to the fact that a different grade of iron is 
desired from that produced in Sweden; that is, in Sweden a metal is 
produced that is low in silicon and carbon and particularly well suited 
to steel making, whereas in California the demand is for a soft gray 
foundry iron. 


IRON. 


85 


As to the advantages of the metal produced in a Swedish type of 
furnace for steel making, they have been stated by Keeney a to he as 
follows: 

1. That it can be converted into steel with greater facility and at a lower cost. 

2. That it admits of greater economy in power consumption. 

3. That it admits of greater economy in reducing material. 

4. That the carbon content can be controlled within a limit of 2.20 per cent maxi¬ 
mum. 

5. That the losses of iron in the slag will not exceed reasonable limits, say 6 per cent 

FeO. 

A metal has been made by the Noble Electric Steel Co., “quite 
similar in both appearance and analysis to the pig iron which was at 
that time reported as being used successfully for steel making in 
Sweden/’ concerning the use of which Crawford b reports as follows: 

Stimulated by the results which were being obtained in Sweden we made consider¬ 
able effort to induce steel makers on the Pacific coast to try it. Finally by making a 
very attractive price we induced one firm to use it. This concern operates both basic 
and acid open-liearths for making concrete reinforcing steel. The report of the works 
superintendent on it was rather indefinite but not enthusiastic. He said “It worked 
pretty well, but normal pig iron was more satisfactory.” Since that time we have sold 
this concern about 1,000 tons of normal low-silicon pig iron and also a few odd carloads 
of white iron which approached in analysis pig steel. They advise that no difference 
is noted in the working of normal electric-furnace pig iron as compared to normal blast¬ 
furnace iron of similar analysis. The pig iron brought the market price, but the pig 
steel always had to be offered on more favorable terms, and even at a reduced price it 
did not call forth any repeat orders. 

These remarks are not intended to be construed as a contradiction of the favorable 
reception which pig steel has been accorded by the Swedish steel men, but it does 
seem to indicate that to gain the advantages claimed pig steel must be used “according 
to prescription” and a good deal of “missionary work” might be necessary before 
American steel makers, who have no patriotic interest in the matter, would do the 

necessary experimenting to prove the advantages claimed. 

✓ 

ENGINEERS’ REPORT OF THE EXPERIMENTAL WORK AT 

TROLLHATTAN. 

The engineers in charge of the experimental work at Trollhattan 
made the following statements in their final report according to the 
Iron and Coal Trades Keview: c 

QUALITY OF PIG IRON PRODUCED IN ELECTRIC FURNACE. 

The silicon content does not vary more than in an ordinary blast furnace. The 
phosphorus content is lower than with the same quality of charge in an ordinary 
blast furnace; tins is due to the lower consumption of charcoal. The percentage 
of sulphur is, however, slightly higher in the electric furnace. But it should be 
observed that both at Trollhattan and at Hagfors unroasted ores have been used with¬ 
out any difficulty arising from the sulphur present. 

a Keeney, R. M., Pig steel from ore in the electric furnace: Bull. Am. Inst. Min. Eng., February, 1914, pp. 
349-367. Discussion, Ibid, J. W. Richards and J. Crawford, p. 1289. 

b Crawford, J., Discussion of paper by R. M. Keeney on “ Pig steel from ore in the electric furnace:” Bull. 

Am. Inst. Min. Eng., June, 1914, p. 1289. 

c Iron and Coal Trades Review, 1913. 




86 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


The quality of the electric pig iron has been highly commended. It acts 
particularly well in the open-hearth furnace, and steel made from it is certainly 
not inferior to steel made from ordinary pig iron. Mr. E. Odelberg, managing director 
of the Stromsnas Iron Works, states that the electric pig iron is “of the very best quality 
for the open-hearth process, and, as regards the uniformity of the silicon content, fully 
as uniform as iron from an ordinary blast furnace.” Mr. A. Herlienus, managing 
director of the Uddeholm Co., states that “the electric pig iron has been used with 
satisfactory results, both for the open-hearth, Bessemer, and the Lancashire processes. 
Generally speaking, there has been no difficulty in obtaining pig iron of uniform 
quality, although slightly better uniformity may possibly be obtained with a very 
carefully conducted blast furnace.” 

It has been found that the proportion of concentrates ought not to exceed 20 per cent 
of the ore charged. This figure, however, does not appear to be final, as in a later and 
somewhat modified furnace of the same type at the Hagfors Iron \\ orks 25 per cent of 
concentrates is used without any difficulty. 

The power consumption per ton of pig iron varies in proportion to the iron content 
in the ore. A poor ore or pig iron high in silicon and manganese requires more power 
than a rich ore or a pig iron low in silicon and manganese. For such iron the power 
consumption averages only 2,067 kilowatt-hours per ton of pig iron; that is, there are 
obtained 4.22 tons of j)ig iron per kilowatt-year, or 3.10 tons per horsepower-year. 

The charcoal consumption per ton of pig iron varies from 20 to 24 hectoliters (56 to 68 
bushels), depending on the quality of the charcoal and the charge. Coke has been 
found to be unsuitable for this furnace unless mixed with charcoal. 

The consumption of electrodes at Trollhattan has been reduced to less than 3 kilo¬ 
grams (6.6 pounds) per ton of pig iron. At Hagfors it has amounted to as much as 6 
to 9 kilograms (13.2 to 19.8 pounds). This discrepancy is explained by the fact that 
the electrode consumption is increased in proportion to the higher power consumption 
for a poorer charge, and is further increased by the more efficient circulation of gases 
and higher CO 2 content in the gas. The lower electric load per unit of surface at the 
Hagfors furnaces also contributes to the higher electrode consumption at this plant. 

The cost of repairs is lower than there appeared at first to be reason to expect. In 
the manufacture of pig iron containing silicon and manganese the costs for repairs 
are higher than in producing pig iron with low contents of those elements. 

VALUE OF GAS PRODUCED. 

At the plant of the Uddeholm Co., at Hagfors, the gas from the furnaces has been 
used with good results for heating the open-hearth furnaces. It has been estimated 
that the value of the gas obtained per ton of pig iron may be taken at 2.50 kroner 
(about 0.42 cent). We quote from the report a summary of the most important figures 
relating to the economical results. These show that step by step the results have 
been improved and the quantity of iron per horsepower-year increased, whereas the 
electrode consumption and time for repairs have been reduced, these three items in 
conjunction with the saving in charcoal being the decisive factors as regards electric 
iron smelting. 

The figures show that during the last few months as much as 3.20 to 3.10 tons of 
iron has been obtained per horsepower-year, whereas before the alterations then made 
the highest average figure was 2.86 tons. The highest expected yield was 3 tons per 
horsepower-year, a figure that has thus been exceeded. It may also be mentioned 
that during single periods of several weeks while especially suitable ores were used 
the highest average figures above mentioned have been materially exceeded. It 
will thus be seen that as regards efficiency the results of the operation of the furnace 
have surpassed expectations. The electrode consumption was 13.8 kilograms (30.4 
pounds), which has finally been reduced to about 3 kilograms (6.6 pounds) per ton of 
pig iron. The cost and time required for repairs could not be estimated beforehand. 


COPPER. 


87 


Experience has shown that both the cost and the time required are less than could 
have been hoped for. Wherever employment for the gas can be found this should 
also be taken into account, as is being done at Hagfors, where its value for firing the 
open-hearth furnaces is estimated to reduce the cost of the pig iron by about 66 cents. 

The results of the work done at Trollhattan in reducing iron ores in 
the electric furnace are summarized in the following table: 

Summary of results obtained at Trollhattan. 


item. 


Ore, concentrates, and briquets, kilograms. 

Limestone, kilograms. 

Charcoal, hectoliters. 

Coke, kilograms. 

Electric energy, kilowatt-hours. 

Iron content of ore, per cent. 

Iron produced, kilograms. 

Slag per ton of iron, kilograms. 

Electrodes per ton of iron, gross, kilograms. 

Electrodes per ton of iron, net, kilograms.! 

Charcoal per ton of iron, hectoliters. 

Working time, hours and minutes. 

Time used in making repairs, hours and minutes... 
Time used in making repairs, per cent of total time 

Average load, kilowatts. 

Time per ton of iron, kilowatt-hours. 

Iron per kilowatt-year, tons. 

Iron per horsepower-year, tons. 


Nov. 15, 
1910, to 
May 29, 
1911. 

Aug. 4, 
1911, to 
June 21, 
1912. 

Aug. 12 
to Sept. 
30, 1912. 

October 
to Decem¬ 
ber, 1912. 

4,338, 338 

7,917,214 

1,406,530 

2,914,830 

345, 405 

647, 479 

108,150 

169,944 

65,474.5 

107, 282.5 
70, 854 
10,845,180 

21,859.5 

44,934.5 

6,339,131 

1,939,073 

3,957, 565 

60.79 

60.75 

68.67 

65.38 

2,636,098 

4,809,670 

965,915 

1,005,865 

350 

324 

192 


10.00 

6.08 

3.02 

2.78 

4.95 

5.17 

3.02 

2. 78 

24.84 

22.31 

22.63 

23.58 

4,441 20 
236 53 

7,218 23 

1,173 8 

2,158 30 

506 7 

13 47 

49 30 

5.06 

6.55 

1.16 

2.24 

1,427 
2.405 

1,502 

1,653 

1,833 

2.255 

2.007 

2.076 

3.64 

3.88 

4.36 

4.22 

2.68 

2.86 

3.20 

3.10 


COPPER. 

PRESENT STATUS OF THE ELECTRIC SMELTING OF COPPER ORES. 

So far as the writers know, the smelting of copper ores in the electric 
furnace is not done commercially in the United States at the present 
time. It is reported, however, that in Norway smelting of copper ores 
with an electric furnace of 750 kilowatts and an estimated capacity 
of 2,000 tons of ore per annum has been tried at the lien Smelting 
Works, Trondhjem, and it is understood that copper ores are to be 
smelted regularly at this plant. A consignment of 25 tons of pure 
copper, the first copper ever produced by electric smelting and 
refining in Norway, was recently exported from the Bitovaria mine 
at Kaafjord, near Dyngor. Some months ago it was reported that 
the electric smelting and refining of nickel and copper would be 
undertaken by a company at Christians and. 

EXPERIMENTAL WORK OF VATTIER, SCHILOWSKI, WOLKOFF, 

AND OTHERS. 

In addition to the work on a commercial scale attempted at Nor¬ 
wegian plants, experimental work on the electric smelting of copper 
ores has been done by Yattier, Schilowski, Wolkoff, Stephan, and the 
writers. Yattier a smelted an ore containing 7 per cent copper and 


a Haanel, E., Report of the commission appointed to investigate the different electro thermic processes 
for the smelting of iron ores and the making of steel in operation in Europe: Canada, Department of Inter¬ 
ior, Mines Branch, 1904, p. 215. 

44713°—Bull. 77—16-7 



































88 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

8 per cent sulphur with the production of a matte containing 47.9 per 
cent copper. Schilowski® smelted mixtures of raw ore and roasted 
ore in an electric furnace and produced a matte. He found that the 
consumption of energy was lowest when the charge contained 60 to 
70 per cent of roasted ore. Using an ore containing considerable 
arsenic, he found it possible to condense the volatilized arsenic in 
chambers. Wolkoff 6 treated a mixture of copper sulphide (Cu 2 S) 
and copper oxide (CuO) in the electric furnace for the production of 
copper by the reaction of the sulphide and the oxide. Stephan c 
smelted oxidized copper ores in the electric furnace for the production 
of metallic copper with charcoal as a reducing agent. In their 
experimental work the writers have smelted native copper concen¬ 
trates and sulphide ores of copper in the electric furnace with favorable 
results. 

In view of the results of the experimental work of the writers and 
others, there seems no good reason why copper-bearing ores can not 
be as successfully treated in an electric furnace as in a combustion 
furnace. In all combustion furnaces used for the treatment of copper 
ores, the fuel takes no part in the reactions necessary for the produc¬ 
tion of the desired product, unless in the reduction of oxide ores 
smelted alone, that is, without a mixture of sulphides, a step that is 
practically unknown in this country at present. For example, in the 
reverberatory furnace the fuel acts only as the heating agent; in 
ordinary blast-furnace smelting, the coke is used to supply the heat 
necessary to raise the temperature so as to permit the necessary 
reactions between the oxides, sulphates, and sulphides of the charge, 
and to scorify the resultant mass, separation of the slag and the 
matte being thus permitted. In partial pyritic and in pyritic 
smelting the necessary oxidation of the sulphides and iron is pro¬ 
duced by the oxygen of the air entering at the tuyeres, and the coke 
used is simply for supplying the amount of heat necessary for carrying 
out the process, which is not supplied by the oxidation of the sulphur 
and the iron present in the charge at the time it passes through the 
tuyere zone of the furnace. Such being the case, there seems to be 
no reason why the smelting of copper ores could not be done just 
as well by electric heat as by that derived from the combustion of 
coke, especially if warranted by local conditions. 

SUMMARY. 

Briefly, then, the electric smelting of copper ores is nothing more 
than the substitution of electric heat for the heat derived from the 

a Schilowski, J., La fusion electrique de cuivre et des produits intermediares de fonderies de cuivre: 
Revue de MiHallurgie, vol. 9,19.12, p. 20.5. 

b Woikoff, W., Electric smelting of copper sulphide ore: Metallurgie, vol. 7,1910, p. 99. 

c Stephan, M., Einiges iiber die Erzeugung von Metallen im elektrischen Ofen: Metall und Erz, vol. 1 
1913, p. 11; Met. and Chem. Eng., vol. 2, 1913, p. 22. 




LEAD ORES AND COMPLEX SULPHIDE ORES. 


89 


combustion of carbon as produced in blast-furnace smelting. In 
some cases the reactions of copper smelting would take place to better 
advantage in the neutral atmosphere of the electric furnace than in 
the reducing or partly reducing atmosphere of the combustion fur¬ 
nace. Therefore as to whether the electric furnace should be used 
for the smelting of copper ores will largely depend on the relative cost 
of coke and electric power. As the use of the electric furnace is not 
advocated as a competitor of the combustion furnace, but as a substi¬ 
tute for it in those localities where it is not advisable because of the 
high cost of fuel to use a combustion furnace, there is no apparent 
reason why the electric furnace may not be developed as a substitute, 
especially in the treatment of copper-bearing ores. In this connec¬ 
tion it is to be remembered that the reason why the electric furnace 
was developed in the iron industry for the reduction of iron from its 
ores was one of necessity. As a matter of fact the field for the electric 
furnace in the reduction of iron from its ores is limited. Perhaps the 
same is true as regards the possible application of the electric furnace 
to the treatment of copper ores, but, judging from the comparative 
costs, it seems that the chances in favor of the electric furnace for the 
treatment of copper ores are greater than those for its use in the 
treatment of iron ores, because there is not so great a difference in 
the cost of coke and electric power in the copper-mining districts as 
in the iron-smelting centers. Also the cost of electric power is con¬ 
stantly becoming less, owing to improvements in gas engines and 
steam turbines, so that in districts where water power is not plenti¬ 
ful, but cheap fuels unsuitable for coke making are available, it may 
be more advantageous to use electric heat than the heat derived from 
the combustion of coke. 

LEAD ORES AND COMPLEX SULPHIDE ORES. 

The smelting of straight lead ores in the electric furnace has seem¬ 
ingly never been attempted either commercially or on a large experi¬ 
mental scale, largely because of the ease and cheapness of smelting 
such ores by combustion processes. For the smelting of ordinary 
lead ores it has no especial application, but in the treatment of com¬ 
plex sulphide ores the electric furnace might be profitably used. 

As stated elsewhere in this report, ores of lead, zinc, and silver are 
being electrically smelted at Trolhattan. During the smelting the 
lead collects in the bottom of the furnace and acts as a collecting agent 
for the silver; the zinc is volatilized and is subsequently condensed. 
In mining districts of the Western States are complex ores of lead, 
zinc, copper, gold, and silver that might be profitably treated in this 
manner, except that if copper were present the process would be 
further complicated by the formation of a matte. With the solution 


90 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

of the zinc-condensation problem in electric-furnace work, it is not 
unreasonable to suppose that such complex ores can be electrically 
smelted with a fair recovery of the base metals, and with a high 
recovery of the precious metals. Also, owing to the fact that practi¬ 
cally as high a temperature as may be desired may be obtained in the 
electric furnace, it would be possible to smelt complex ores that are 
high in gold and silver content but low in base metals, such as lead 
and zinc. Such recovery would be worth the additional expense of 
wet concentration. In the blast furnace 10 per cent of zinc in the 
charge causes sticky slags, and a much higher percentage makes the 
operation of the furnace irregular and difficult. Such slags can be 
fused readily in an electric furnace. If the ore contained copper and 
zinc, the ore could be charged into an electric blast furnace, matte 
being used as an agent for collecting the gold and silver. 

GOLD AND SILVER ORES. 

In the smelting of gold and silver ores carrying no lead or copper to 
form either a lead bullion or a copper matte, but containing iron sul¬ 
phide, the electric furnace might be used in connection with an air 
blast for oxidation of the iron sulphide, an iron matte being used as a 
collecting agent for the gold and silver. The value of iron matte as a 
collecting agent is still largely a matter of personal opinion, but from 
the pyritic smelting done with iron as a collecting agent and from 
some of the writers' experiments in wiiich iron matte was used in the 
electric furnace, it is evident that a fair recovery can be made in this 
way. As in electric copper smelting, the electric-furnace treatment 
of these ores is still in the experimental stage. 

Recently a plant has been installed at Lluvia de Oro, Chihuahua, 
Mexico, for the electric melting of zinc cyanide precipitate and the 
smelting of ore concentrates.® The gold-silver bullion resulting is 
shipped and the slag resmelted or concentrated. The process 
appears to be successful in this application. 

The writers believe that at many mines in isolated districts wdiere 
fuel is usually high and wdiere hydroelectric power is used for the 
mine or mill, the cyanide precipitates could be melted more econom¬ 
ically in electric furnaces than in combustion furnaces. The con¬ 
struction of a small furnace of the Siemens type is simple and inex¬ 
pensive. By using the electric furnace when one of the units of the 
mill is idle for repairs or during the mine shift when little hoisting or 
drilling is being done, no additional electrical installation would be 
necessary. Thus, pow r er that under ordinary conditions is wasted 
wall be utilized. 


a Coulslin, H. R., Electric furnace at Lluvia de Oro: Eng. and Min. Jour., vol. 93, 1912, p. 1189. 



ZINC. 


91 


ZINC. 

In the metallurgy of nonferrous metals the electric furnace has had 
a greater application for the treatment of zinc ores than in the metal¬ 
lurgy of any of the other nonferrous metals except aluminum. Since 
1885, when an elec trie furnace for the treatment of zinc ores was patented 
by the Cowles brothers, experimental work has been done. However, 
the process has not been applied to any great extent because of the 
difficulty of condensing the zinc vapor produced in smelting in the 
electric furnace. The cause of this difficulty has not yet been defi¬ 
nitely determined. With few exceptions the work has not been done 
on a very large scale, and so it may be said that the electric smelting 
of zinc ores is still in the experimental stage. 

Undoubtedly there is an inviting field for the electric furnace in the 
metallurgy of zinc, but before its wdde application can be expected the 
condensation problem and various mechanical problems must be 
solved. The latter should not prove difficult. The special field for 
electric-furnace work in zinc metallurgy is due largely to the low 
thermal efficiency of the present zinc retort, which is given by Rich¬ 
ards ° as only 7 per cent. 

As the efficiency of the electric furnace is 50 to 75 per cent, the 
difference in the heat necessary for carrying out the smelting opera¬ 
tion is so great as to permit a higher cost of electrical energy than is 
permissible in many electrometallurgical operations. 

In this report the writers discuss broadly and briefly the present 
methods of retort smelting, experimental work on the electric smelting 
of zinc ores, and the present status of electric zinc smelting. The Bu¬ 
reau of Mines is investigating the electrometallurgy of zinc ores, and 
the results of experimental work, together with a complete resume of 
literature on the subject, will be presented at a later date. 

PRESENT METHODS OF ZINC SMELTING. 

Briefly, the present method of zinc smelting consists of the roasting 
of sphalerite (ZnS) to zinc oxide (ZnO). The roasted ore is then 
smelted wdth excess carbon as a reducing agent in a closed fire-clay 
retort having a condenser attached. The zinc oxide is reduced to zinc 
at a temperature of 1,033° C. and as the boiling point of zinc, accord¬ 
ing to various authorities, is from 920° to 930° C., the reduced zinc 
passes off as a vapor and is condensed as liquid metal in a condenser. 
In order to make the reaction more rapid the temperature of the retort 
is kept at 1,100° to 1,300° C. 

Zinc vapor condenses into a liquid mass in the range of temperature 
from 420° to 860° C. The lower temperature is that of solidification 
of zinc, and the upper approaches the vaporization point. In practice 


a Richards, J. W., Metallurgical calculations, pt. 1, 1906, p. 80. 




92 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

it is the aim to keep the temperature at 500° C., so that the zinc can 
be tapped off molten from the retort. If the temperature of the con¬ 
denser is too low the vapor is too dilute, or if the vapor is diluted with 
some carbon dioxide instead of carbon monoxide, or with metallic 
vapors other than zinc, there will be a formation of blue powder, which 
consists of minute particles of zinc, each particle seemingly covered 
by a thin coating of zinc oxide. Because of this coating of oxide the 
powder can not be converted to spelter by simple melting. 

The process is intermittent and a retort holds only about 200 
pounds of mixture. A charge is smelted, the zinc removed from the 
condenser, and the residue raked out of the retort. Because of the 
small scale and intermittent nature of the operation the labor cost is 
high. Likewise the thermal efficiency is low because of the heat 
being conducted to the charge through the furnace walls. The retorts 
are an expensive feature of the process, as at the high temperature 
necessary they last only about a month. 

ZINC SMELTING IN THE ELECTRIC FURNACE. 

Processes for the electric smelting of zinc ores are of twx) general 
classes—first, reduction of the zinc oxide and its compounds by car¬ 
bon and carbon monoxide, and, second, decomposition of the sulphide 
by metallic iron. Examples of the first method are the De Laval and 
Johnson processes, and of the latter, the Cote-Pierron and Imbert- 
Thomson-Fitzgerald processes. Reduction of zinc oxide with carbon 
is based upon the reactions 

ZnO + C=Zn+CO 
Zn0+C0=Zn+C0 2 
C0 2 + C=2 CO 

The use of iron is according to the reaction 

ZnS 2 +Fe=Zn+FeS 2 

In neither of these processes does the electric current perform any 
function other than heating. As alternating current is supplied to 
the furnace, there is no electrolysis. As is shown later, the process 
may be performed in either an arc or a resistance furnace. 

One essential difference between the reduction of zinc oxide with 
carbon in an electric furnace and in the retort is that the retort process 
is intermittent, whereas the electric process may be continuous. In 
the electric furnace the charge is added at intervals, as may be neces¬ 
sary, and the slag is tapped or allowed to run continuously from the 
furnace without disturbing the operation of the process. The reduc¬ 
tion by carbon or carbon monoxide occurs as in the retort, except 
that owing to the rapidity of reduction in the electric furnaces as at 
present designed the third reaction seemingly does not take place as 
well in the electric furnace as in the retort, so that the zinc vapor con- 


ZINC. 


93 


tains more carbon dioxide, which has a bad effect on the condensa¬ 
tion and results in the production of a large amount of blue powder. 
A arious attempts have been made to obviate this evil, the principal 
one being the passing of the vapor through incandescent carbon 
before it enters the condenser. 

ELECTRIC ZINC SMELTING AT TROLLHATTAN AND SARPSBORG. 

The largest plant in commercial operation for the electric smelting 
of zinc ores is that of the Norse Power & Smelting Syndicate at 
Trollhattan, Sweden, which also has a smaller works at Sarpsborg, 
Norway. 

EQUIPMENT AT THE TWO PLANTS. 

The Trollhattan plant has a furnace house 300 by 52 feet, which 
contains 11 resistance furnaces, 6 on one side of the building and 
5 on the other. There are also two refining furnaces and several 
arc furnaces. In 1912 it was reported that the new furnace house, 
then partly erected, was to contain eight furnaces of 600 to 900 kilo¬ 
watts each. The old furnaces each have a capacity of 270 kilowatts. 
The total power now being used at the works is 3,000 kilowatts, and 
with the new installation it will be 7,500 to 10,000 kilowatts. 

The Sarpsborg plant has three arc furnaces and four refining 
furnaces. 

For the past six or seven years zinc smelting has been conducted 
at these works in the De Laval furnace, but part of the product has 
been the result of refining dross and scrap. It is stated that now ore 
smelting, in which carbon is used as a reducing agent, is being carried 
on and that regular shipments of finished zinc were made during the 
year 1912. The only information available about the works is con¬ 
tained in Harbord’s report a published in 1911, as everything in 
regard to the process and the results obtained is kept as secret as 
possible. 

SMELTING PROCESS. 

The smelting process consists essentially of two operations, con¬ 
centration of the zinc to a rich oxide, followed by reduction in another 
furnace. Oxide ore, flux, and carbon used as reducing materials, are 
charged into the furnace, where most of the zinc and some of the lead 
are volatilized and condensed, partly as metal and partly as blue 
powder and oxide, containing 54 per cent zinc and 20 per cent lead- 
This is really a concentration process, for the blue powder is subse¬ 
quently mixed with ore and recharged, when a larger percentage of 
the metal volatilized is recovered as metal. The remainder of the 
lead, which carries some silver, is reduced to metal in the smelting 
hearth and is tapped with the slag. Some lead, zinc, and silver passes 
into the matte and some into the slag. 


a Harbord, F. W., Zinc smelting at Trollhattan: Eng. and Min. Jour., vol. 93„ 1912, p. 344. 



94 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

Each furnace is of a modified Siemens type with a shallow hearth 
and covered with a roof. A carbon block bottom forms one electrode 
and the other passes vertically through the roof. ' In some furnaces 
the ore is charged through the roof, in others at one side of the elec¬ 
trode, whereas others have been designed having a continuous side 
feed. Three-phase current is transformed from 10,000 volts to 110 
volts at the furnaces. The furnaces are connected one to a phase. 
The capacity of a 270-kilowatt resistance furnace is 2.8 tons of ore 
per 24 hours. Each furnace holds about 3 tons. A condenser is 
attached to each furnace. 

The charge used by Harbord consisted of 600 pounds of roasted 
Broken Hill slime, 22 pounds of calamine, and 165 pounds of coke. 
Broken Hill slime averages 32 per cent zinc, 23 per cent lead, and 25 
ounces per ton silver. The powder resulting from this charge was 
resmelted in another furnace, the charge being 220 pounds of roasted 
Broken Hill slime, 440 pounds of powder, 55 pounds of coke dust, and 
11 pounds of lime. Three furnaces were operated on ore mixture, 
and four furnaces on ore-powder mixture. At the end of the second 
day the ore furnaces were making sufficient powder to supply the 
powder furnaces. The furnace condensers were tapped every four 
hours for crude zinc and powder, and the slag, matte, and lead were 
tapped about every eight hours. 

RESULTS OF OPERATION OF FURNACES. 

During the first part of the run the slags were not clean because of 
imperfect separation of matte and slag. This fault was caused by 
the use of too basic a slag and by imperfect mixing of the charge. 
Toward the end of the work this was improved considerably. There 
was also considerable trouble experienced in changing electrodes, 
owing to defective mechanical apparatus, a difficulty that could easily 
be remedied in a new plant. There were no serious stoppages caused 
by failure of the furnaces. 

In 27.58 days the seven furnaces smelted 578 metric tons of roasted 
Broken Hill slimes, 19 tons of calamine, and 22.5 tons of blue powder 
from stock. From this material there was produced 160.8 tons of 
crude zinc and 36 tons of powder. At the end of the run there was 
13.4 tons more powder on hand than at the beginning. The crude 
metal averaged 79 per cent zinc, 20 per cent lead, and 0.6 per cent iron. 
From this there was produced on refining 112.4 tons of spelter con¬ 
taining 99.9 per cent zinc and 24.7 tons of lead. The lead tapped 
with the slag was remelted to remove the slag. This yielded 41 tons 
of marketable bullion, containing 141 ounces of silver per ton. There 
was also obtained 17 tons of leak lead, assaying 27 ounces silver per 
ton. In addition there was 9 tons of skimmings which contained 
lead, zinc, and silver. The total input of metals was 204.04 tons of 


ZINC. 


95 


zinc, 128.35 tons of lead, and 15,750 ounces of silver. Thus with 537 
tons of ore charged the charge averaged 38.1 per cent zinc and 24 per 
cent lead. The extraction as metals was 130.46 tons of zinc, 94.94 
tons of lead, and 7,230 ounces of silver. The yield as metals was then 
64 per cent zinc, 73.99 per cent lead, and 45.9 per cent silver. In¬ 
cluding the metals in the powder left the yield was 73.4 per cent 
zinc, 79.3 per cent lead, and 49.5 per cent silver. 

At the Sarpsborg plant the electrothermic-refining results on the 
crude spelter from the powder furnaces were as follows: Fine zinc 
83.9 per cent, powder 9.8 per cent (corresponds to 8.8 per cent metals), 
residues of lead, etc., 2.2 per cent, charge in furnace 1.1 per cent, 
impregnations in brick walls of furnace and condenser 0.5 per cent, 
unaccounted for 3.5 per cent, total 100 per cent. The effect of a new 
lining is shown by the loss unaccounted for, being 5.7 per cent at 
Trollhattan during the experimental run, as compared with 3.5 per 
cent in regular running at Sarpsborg. 

The consumption of electric current in the experimental run at 
Trollhattan averaged 2,078 kilowatt-hours per ton of ore smelted, 
which does not include current used in resmelting the powder. Two 
tons of powder was retreated per ton of ore smelted. A comparison 
of the resistance furnaces at Trollhattan with the arc furnaces at 
Sarpsborg shows that while one was as good as the other for producing 
the desired reaction, the energy consumption was 70 per cent more 
in the arc than in the resistance furnace. The consumption of elec¬ 
trodes was also higher in the arc than in the resistance furnace, being 
89.2 pounds' per ton of ore at Sarpsborg and 69.3 pounds per ton at 
Trollhattan. 

COMMENTS BY HARBORD AND MOULDEN. 

N 

Regarding the process, Harbord a reports as follows: 

The weak point of the process is the large amount of metallic powder produced in 
proportion to the metals. The recovery of a large percentage of metals is admittedly 
a very difficult problem, but that present practice can be very greatly improved upon 
I have not the least doubt, leading to decreased consumption of energy and reduction 
of labor costs. One detail which is a great improvement on the early practice is the 
better separation of the crude zinc from the powder by a mechanical stirrer. 

At the time Harbord made his report, J. C. Moulden, 6 who is con¬ 
nected with a company (the Sulphide Corporation) that ships the 
Broken Hill slimes used at Trollhattan, stated that he was of the 
opinion that the extraction, after certain improvements should be 
made, would eventually be 75 per cent zinc, 80 per cent lead, and 80 
per cent silver. 

The cost of power at Trollhattan is about $10 per kilowatt-year or 
0.11 cent per kilowatt-hour. 


a Harbord, F. W., Zinc smelting at Trollhattan: Eng. and Min. Jour., vol. 93,1912, p. 344. 
b Met. and Chem. Eng., vol. 9,1911, p. 673. 




96 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

EXPERIMENTS AT M’GILL UNIVERSITY. 

For several years extensive experimental work on a laboratory 
scale has been conducted under the direction of Dr. Alfred Stansfield 
and Mr. W. It. Ingalls.® This experimental work has been largely 
directed toward a study of the condensation problem and the speed 
of reduction. Uncommonly high percentages of carbon dioxide were 
found in the gases from the electric furnace, which, as previously 
stated, prevents condensation of the zinc as metal by oxidizing the 
condensing globules of the zinc and preventing coagulation. Other 
experimenters have noted this difficulty, as well as the presence of 
considerable quantities of carbon and ore dust in the condenser. 
The latter are believed to be due to the stirring up of dust in feeding 
the charge into the furnace. 

Experiments were also conducted on the reduction of zinc oxide 
in an intermittently heated retort. The charge was introduced into 
the retort at the beginning of the operation and at the end the residue 
was discharged as an unfused residue. Reduction took place slowly 
and the results obtained showed that although it might have been 
possible to operate the process continuously, such a course was not 
feasible. When the furnace was started with a bath of slag and the 
charge introduced continuously upon the bath, the reduction became 
relatively rapid. No explanations were given for this increase, but 
Ingalls states that a retort of small proportions smelts a surprisingly 
large quantity of charge by comparison with the retort of ordinary 
practice at an equivalent temperature. With a furnace consisting of 
a plumbago crucible 12 inches in diameter, 10 pounds of ore per hour 
was smelted. With a furnace 18 by 18 inches in horizontal section, 
737 pounds was smelted in 23 hours. However, the statements as 
published are not complete. The output of an electric furnace is 
due chiefly to the energy input and not to the interior volume of the 
furnace. The capacity in kilowatts of the furnaces used is not given, 
but it is clear that, in comparison with a combustion retort, the 
electric furnace has a high output per unit of interior volume. 

As the electric furnace may have a high temperature, most of the 
zinc may be driven off, a low zinc slag being left to be tapped from 
the furnace. A calcareous slag as well as a high temperature is also 
necessary. In the experiments at McGill University, the slags con¬ 
tained less than 1 per cent of zinc. 

Interesting figures of power consumption were obtained in the 
experiments at McGill. In one run lasting 24 hours, with a resistance 
furnace 18 by 18 inches, the power consumption was 1,610 kilowatt- 
hours per short ton of ore smelted. Theoretically it is estimated 
that 955 to 1,060 kilowatt-hours per short ton of ore is necessary to 


a Ingalls, W. R., The electric smelting of zinc ores: Eng. and Min. Jour., vol. 94, 1912, p. 7. 




ZINC. 


97 


smelt ordinary zinc ore. Ingalls concluded that a figure of 1,200 
kilowatt-hours per short ton would be ample. He also concluded 
that there is some chance for electric zinc smelting if such smelting 
can be done with 1,200 kilowatt-hours per ton of ore, if the labor and 
electrode costs can be reduced materially, and if 90 per cent of the 
metals can be extracted. 

Previous to the experiments of Stansfield and Ingalls, Stansfield 
and Reynolds conducted experiments on the smelting of lead and 
zinc sulphide ores carrying silver, with the intention of distilling and 
condensing the zinc, and reducing the lead in the molten form, thus 
collecting the silver. The experiments showed the possibility of 
smelting the ores in the manner indicated, and the extraction of lead 
was particularly satisfactory. The later work of Stansfield and 
Ingalls verified the former results and ores of this class are now being 
treated at Trollhattan. 

EXPERIMENTS OF JOHNSON. 

One of the most persistent investigators of the electric smelting of 
zinc ores is W. M. Johnson,® who has conducted experiments on a 
large laboratory scale for several years. His furnace has vertical 
upper electrodes of carbon and a carbon conducting hearth. The ore 
is fed through the roof of the smelting chamber. There are several 
tap holes at different levels. The zinc vapor passes through a flue 
into an adjacent column of carbon which is heated by the passage of 
the electric current. During the downward passage of the vapor 
through the hot carbon, the carbon dioxide is supposed to be reduced 
to monoxide. The vapor then passes into a condenser, where most 
of the zinc is condensed as metal and some as blue powder. The 
furnace is operated continuously. The ore is preheated by gas to 
900° C. before entering the electric furnace. 

Except for a few statements, the information printed about the 
work done by Johnson does not clearly show the extent to which he 
has carried condensation without the formation of blue powder, but 
the use of a column of hot carbon to reduce the carbon dioxide in the 
vapor seems to have helped to lower the percentage of blue powder 
formed. 

ELECTRIC SMELTING OF ZINC SULPHIDE ORES WITH IRON AS A 

DESULPHURIZING AGENT. 

The two chief exponents of the use of iron as a desulphurizing agent 
in the electric smelting of zinc sulphide are the Imbert and Cote- 
Pierron processes. Imbert tested the reaction, without much success, 
in the combustion furnace. Thomson and Fitzgerald later designed 
an electric furnace for its application. 


a Johnson, W. M., Notes on electric zinc smelting: Met. and Chem. Eng., vol. 10,1912, p. 537. 





98 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

Although the Imbert-Thomson-Fitzgerald process has been tried 
experimentally on a seemingly large scale for two years in Upper 
Silesia, little authoritative information has been issued concerning it. 
Several types of resistance furnace have been used, all having a resistor 
of solid carbon. 

The Cote-Pierron process® uses a furnace of the Siemens type, or 
one having the two vertical electrodes in series, both types being 
roofed and connected with a column of electrically heated carbon, 
through which the vapor passes before going to the condensing 
chamber. 

The same trouble has been experienced in using iron as in using 
carbon for reduction of the zinc oxide, namely, the proportion of 
blue powder formed. It seems that iron and iron sulphide are 
volatilized and that other vapors are given off which dilute the zinc 
vapor and cause trouble in the condensation of the zinc. Even with 
the column of carbon of the Cote-Pierron process this trouble con¬ 
tinued. Moreover, the Cote-Pierron process does not appear to 
have developed into the commercial success it was expected to be. 

Although it is claimed that the use of iron as a desulphurizing 
agent in the direct treatment of sulphide ores avoids roasting, it is 
probable that any saving thus effected is more than offset by the 
cost of ron. For carrying out the reaction, about 700 pounds of 
iron is stated to be necessary per ton of 30 per cent zinc ore. At $12 
per ton the cost of iron would be about $4 per ton of zinc sulphide ore 
treated. The cost of roasting a zinc sulphide ore is estimated by 
Ingalls at $1.25 to $1.75 per ton. It is doubtful whether a regener¬ 
ative process for recovering the iron from the iron sulphide formed 
would be successful, or cheap enough to reduce the cost below that 
of roasting. The zinc sulphide might be sold if a market was near, 
but it probably would be contaminated by other metals in the ore. 

PRESENT STATUS OF ELECTRIC ZINC SMELTING. 

Although, as previously stated, more progress has been made to 
date in the electric smelting of zinc ores than with the electric smelt¬ 
ing of any of the nonferrous metals except aluminum and metals 
forming ferro-alloys, such as silicon, chromium, and tungsten, never¬ 
theless the process is still largely in the experimental stage. There 
is no plant operating on a commercial scale except the Trollhattan 
works, which take 7,500 to 10,000 kilowatts. The experimental 
work continues, but as yet none of it has developed a commercial 
operation. 

It was recently reported that the Sulphide Corporation had con¬ 
structed, at Cockle Creek, New South Wales, an electric zinc smelting 


a Fleurville, E., Electric zinc smelting: Met. and Chem. Eng., vol. 7,1909, p. 468. 




ZINC. 


99 


plant, combined with a plant for the manufacture of sulphuric acid 
and superphosphate. The plant was supposed to be ready for opera¬ 
tion in June, 1913, but no later information has been received. 

DIFFICULTY OF CONDENSING ZINC VAPOR INTO METAL. 

From what has been said concerning the work at Trollhattan and 
the results of others, it is evident that the difficulty lies almost en¬ 
tirely in the condensation of the zinc vapor into metal rather than 
with the formation of blue powder under the peculiar conditions of 
the electric furnace. The electric furnace, mechanically or electric¬ 
ally, presents no great difficulties, because all of the troubles formerly 
experienced have been solved in the construction of large pig-iron, 
steel, carbide, and ferro-alloy furnaces. The problem, then, is one of 
a metallurgical nature and is caused by the different conditions and 
greater speed of smelting in the electric furnace than in the com¬ 
bustion retort. 

THE ELECTRODE PROBLEM. 

The opponents of the electric smelting of zinc ores, who as a rule 
appear to have no knowledge of the great development of the electric 
furnace itself in the treatment of other ores, often state that although 
the retort is the weak part of the old system, so is the electrode of 
the electric method. Judging from large-scale electrometallurgical 
work on other ores the authors do not believe that in general the 
electrode is an exceptionally weak part of electric smelting. The 
electrode problem is no longer serious in iron smelting, and in other 
electric-furnace work. It is only fair to assume that the designer 
of an electric zinc smelter should stand on the shoulders of accumu¬ 
lated knowledge and utilize the results of others when the metallur¬ 
gical problems of electric zinc smelting have been solved. 

RETORT AND ELECTRODE CONSUMPTION. 

Although it is not the purpose of the writers to enter into a discus¬ 
sion of the relative advantages of processes, it may be of interest to 
present a few comparative facts regarding retort and electrode con¬ 
sumption. 

Ingalls® states that during a period of ten years the average life 
of a Silesian retort was 38 days. One charge was melted per day. 
The Silesian retort is said to take 200 pounds of ore per charge. * 6 
Hence a retort treats 7,600 pounds or 3.8 tons of ore. Ingalls 0 also 
states that a condenser lasts 8 to 12 days, so that about four conden¬ 
sers are necessary for the ore smelted by a single retort. He als o 
states that a seasoned retort is valued at 50 cents and a condenser at 


a Ingalls, W. R., The metallurgy of zinc, p. 545. 

& Editorial: Eng. and Min. Jour., vol. 94, Dec. 14,1912, p. 1109. 
c Ingalls, W. R., op. cit., p. 242. 



100 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

4 cents. Thus, the cost of a retort and condensers for smelting 3.8 
tons of ore is 66 cents, or 17 cents per ton of ore smelted. 

At Trollhattan, Sweden, the electrode consumption has been re¬ 
duced to 6 pounds per ton of pig iron produced. Considering that 2 
tons of ore was charged for each ton of pig iron produced, the con¬ 
sumption per ton of ore is 3 pounds. The smelting conditions in elec¬ 
tric iron reduction would not tend to be as strongly reducing as in the 
zinc retort, although the ore in each case would be an oxide. Hence 
it may be expected that the total consumption of electrodes in a 
large properly designed zinc furnace will not exceed 3 pounds per ton 
of ore. There is no longer loss of electrode because of unconsumed 
ends, as that loss has been entirely overcome by jointing both amor¬ 
phous-carbon electrodes and graphitized electrodes. This procedure 
reduces the loss by one-half. In some experiments by the writers 
on a mixture of sulphide and oxidized copper ores with no carbon in 
the charge and the charge proportioned so as to contain 15 per cent 
sulphur, the electrode consumption with air blown into the furnace 
for partial pyritic smelting was only 2 pounds per ton of ore. How¬ 
ever, the furnace was designed so that the charge protected the elec¬ 
trode from the air. Amorphous-carbon electrodes can be obtained 
at 3 to 4 cents per pound, so that on the basis of a consumption of 3 
pounds per ton of ore the electrode cost would be 9 to 12 cents, as 
compared with a retort cost of 17 cents. These figures seem to show 
that the retort at the present time is the weaker. 

THE FUNDAMENTAL DIFFICULTY. 

Then, if the failure of the electric furnace in smelting zinc ores is 
not due to the electric furnace nor the electrodes, what is the metal¬ 
lurgical condition that causes condensation difficulties and has 
retarded the commercial application of the process? The difficulty 
is of course due to a difference in the smelting conditions of the elec¬ 
tric furnace as compared with the retort. Both physical and chem¬ 
ical conditions influence the formation of blue powder. Some pow¬ 
der forms under certain conditions of pressure and temperature. 
Just what these conditions are has not been determined. The prob¬ 
lem is one for the physical chemist. The formation of blue powder 
is due largely to the speed of reduction of zinc oxide in the electric 
furnace and to the presence of volatile impurities in the charge. 
Boudouard found that the permissible percentage of carbon dioxide 
in the zinc retort was low, and that when the limit was exceeded the 
carbon oxidized the zinc, causing the formation of the blue powder. 
The vapor of the zinc retort is usually below this limit or not much 
above it, so that the zinc is condensed chiefly as liquid zinc. But in 
the electric furnace, the temperature directly beneath the electrode in 
either the arc or the resistance furnace is so high that the reduction 


TIN. 


101 


proceeds rapidly and the large amount of carbon dioxide formed 
does not have a chance to be reduced to monoxide by the hot coal 
of the charge before entering the condenser. Hence, there is the 
oxidation of the zinc mentioned. By the use of electrodes of large 
cross section, it is probable that this concentrated heating could be 
reduced, so that rather than a high temperature at one place there 
would be a uniform comparatively low temperature all over the 
charge. This was found to be the case in the smelting of iron ores 
both at Heroult, Cal., and Trollhattan. Or the current could pos¬ 
sibly be distributed more evenly by flat electrodes of rectangular 
cross section. The formation of blue powder is also caused by vola¬ 
tilization of silicon which condenses on the zinc either as silicon or 
silica. For example, in some experiments at the Bureau of Mines 
laboratory, the condensed fumes from a ferrosilicon furnace contained 
67.69 per cent Si0 2 , 9.72 per cent A1 2 0 3 , 4.11 per cent FeO, 0.20 per 
cent MgO, 1.90 per cent CaO, with the rest carbon. This vola¬ 
tilization of silicon occurs in any electric furnace operated with an 
arc, as in ferrosilicon manufacture, when there is silica in the charge. 
At the lower temperature of a resistance furnace it is not so likely 
to occur. 

This problem, although difficult, should be solved in time. When 
it has been solved and there is no need of resmelting a large propor¬ 
tion of blue powder as at Trollhattan, where 2 tons of blue powder is 
smelted for each ton of ore treated, it is probable that electric zinc 
smelting will proceed rapidly. The use of iron as a desulphurizing 
agent does not seem to have advanced as far as reduction of the oxide 
with carbon, and it is probable that the latter method will keep its 
present supremacy. Some work has been done in an electric furnace 
operated under pressure or vacuum, but only a beginning has been 
made in this direction. 

TIN. 

Although rather extensive experiments have been conducted in 
England on the smelting of tin ores in the electric furnace,® the 
authors know of no place where the electric furnace is being used for 
that purpose at the present time. Moreover, as only small quantities 
of tin ore have ever been found in the United States or its possessions, 
the use of the electric furnace for the smelting of tin ores will not be 
discussed. 


a Harden, J., Electric tin smelting: Met. and Chem. Eng., vol. 9,1911, pp. 453-457. 




PART III. THE MANUFACTURE OF FERRO-ALLOYS IN 

THE ELECTRIC FURNACE. 


By Robert M. Keeney. 


INTRODUCTION. 

The subjects presented in this part of the report include an account 
of the development of the manufacture of ferro-alloys in the electric 
furnace, descriptions of some types of electric furnaces used in ferro¬ 
alloy production, descriptions of several European plants that have 
been visited by the writer, and information regarding the manufac¬ 
ture and uses of each ferro-alloy. 

A ferro-alloy is an alloy of iron so rich in some element other than 
carbon that the alloy is used primarily as a vehicle for introducing 
that element into the manufacture of iron and steel. Ferro-alloys 
are not usefully malleable, and they usually contain more of the 
alloying element than is desirable in an alloy steel. 

Ferro-alloys may be used in the manufacture of iron and steel in 
two ways. First, the ferro-alloy may be added to the steel for its 
cleansing and deoxidizing effect with the intention that the alloying 
element will combine with oxygen or some other impurity in the 
steel bath and pass either wholly or for the greater part into the slag. 
Second, the ferro-alloy may be used as a fixed addition, the alloying 
element staying in whole or for the greater part in the steel, to which 
it imparts some desirable quality. 

The problem encountered in the manufacture of ferro-alloys has 
been the production of an alloy with a low percentage of carbon, a 
high percentage of the alloying element, and a low percentage of im¬ 
purities that might be injurious to steel. The alloy should have a 
low enough melting point so that it can be used in a steel bath of 
ordinary temperature. To obtain this feature it has been necessary 
in some cases to produce an alloy with a high percentage of carbon 
and a comparatively low percentage of the alloying element. The 
ferro-alloys with a low percentage of carbon are considerably more 
expensive than the high-carbon alloys, because of the extra refining 
necessary, which requires a higher power consumption and increased 
quantities of expensive ores for deoxidization. It is also essential 
to produce a ferro-alloy of uniform composition, a difficult feature 
with some alloys. A ferro-alloy that is not uniform is a source of 
102 




EARLY DEVELOPMENT OF MANUFACTURE OF FERRO-ALLOYS. 103 

trouble and expense in the manufacture of alloy steel, because it is 
not possible to regulate closely the composition of the steel produced. 
How these points have influenced the development of the manufac¬ 
ture of ferro-alloys is shown in the following discussion. 

The most important ferro-alloys in order of their use are ferro¬ 
manganese, spiegeleisen, ferrosilicon, ferrochrome, silicomanganese, 
ferrotitanium, silicomanganese-aluminum, ferrotungsten, ferrovana- 
dium, ferronickel, and ferrophosphorus. Other alloys not so widely 
used but employed by some steel makers are ferrocobalt, ferrosilicon- 
aluminum, silicocalcium-aluminum, and ferromolybdenum. Other 
ferro-alloys that have been investigated by the manufacturers but 
for which no wide use has as yet been found are ferroboron, ferro- 
uranium, and ferrotantalum. 

EARLY DEVELOPMENT OF THE MANUFACTURE OF 

FERRO-ALLOYS. 

DEVELOPMENT PREVIOUS TO THE USE OF THE ELECTRIC 

FURNACE. 

Up to the year 1899, when the electric furnace was first used for 
the manufacture of ferro-alloys, all such alloys were made in the 
blast furnace or the crucible furnace. Ferromanganese with a high 
percentage of manganese was first produced at Bonn, Germany, in 
1886.® This alloy was made in a crucible and contained 70 to 80 per 
cent manganese. In 1873 the manufacture of ferromanganese was 
first conducted in the blast furnace, a method by which the greater 
part is manufactured to-day. In 1875 ferrosilicon containing 10 to 12 
per cent silicon was made in the blast furnace. The manufacture of 
ferrochrome in a commercial way in the blast furnace was started in 
1886. Thus up to the year 1890 the only method of manufacture of 
ferro-alloys was the use of the crucible, the blast furnace, or occa¬ 
sionally the open hearth. In every case carbon in the form of coke 
or anthracite coal was used as a reducing material. 

The production of a ferro-alloy with a low carbon content or a high 
percentage of the alloying element is limited in the blast furnace by 
three difficulties—first, the temperature is too low for the reduction 
of some of the oxides of the alloying metals, so that only alloys of 
metals reduced at a comparatively low temperature or of low melting 
point can be made; second, it is difficult to obtain an alloy containing 
a high percentage of the special metal; and third, it is impossible to 
produce a ferro-alloy low in carbon because of the great excess of 
carbon in the charge. 

With the crucible, owing to the small scale of operation necessary, 
the process is necessarily expensive. Owing to the temperature 

a Venator, W., liber Eisen Liegierungen und Metall fur die Stahl Industrie: Stahl und Eisen, vol. 28, 
1908, p. 41; Iron and Coal Trade Rev., vol. 76,1908, p. 520. 

44713°—Bull. 77—16-8 





104 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

limitation, certain oxides can not be reduced and metals of high 
melting point can not be melted; it is difficult to obtain an alloy 
with a high percentage of the special metal; and if a graphite crucible 
is used, the percentage of carbon tends to be high in the ferro-alloy. 

For these reasons, up to 1890 the manufacture of ferro-alloys was 
mostly confined to the production of ferromanganese of 70 to 80 per 
cent manganese, ferrosilicon of 10 to 12 per cent silicon, and ferro- 
chrome of 30 to 40 per cent chromium and of 6 to 12 per cent carbon. 

INTRODUCTION OF THE ELECTRIC FURNACE. 

The opportunity for improvement in the production of high-grade 
ferro-alloys by the use of the electric furnace was made evident by the 
researches of Moissan,® beginning in 1890, upon the reduction of 
metallic oxides in the electric furnace. Moissan used an arc furnace, 
consisting of a chamber of refractory material, into which two hori¬ 
zontal carbon electrodes were introduced. 

The commercial production of ferro-alloys in the electric furnace 
began in 1899, when the Bullier patents for the manufacture of calcium 
carbide were declared valid in France. There was also an overpro¬ 
duction of calcium carbide, which culminated at the same time. The 
overproduction rendered it necessary for many established carbide 
works to seek new uses for their electric power and electric-furnace 
installations. Those works began the manufacture of ferrosilicon, 
ferrochrome, and ferromanganese in their old carbide furnaces. At 
that time the manufacture of ferromanganese in the electric furnace 
did not prove successful because of the high loss by volatilization, and 
it was abandoned. The production of high-percentage ferrosilicon, 
ferrochrome, and other ferro-alloys not easily volatilized was very 
successful. 

By 1902 ferrosilicon containing 25 per cent silicon was being used 
to a considerable extent instead of the blast-furnace alloy of 10 to 12 
per cent silicon. This development was quickly followed by the 
introduction of ferrosilicon containing 50 per cent, 75 per cent, and 90 
per cent silicon. The high-grade ferrochrome of 60 to 70 per cent 
chromium content and 5 to 8 per cent carbon rapidly replaced the 
blast-furnace product of 30 to 40 per cent chromium and 6 to 12 per 
cent carbon. Later the production of ferrochrome containing less 
than 1 per cent carbon was begun. As the refining possibilities and 
high temperature available in the electric furnace were more fully 
appreciated, the production of many ferro-alloys not previously made 
began. Also in recent years, by careful control of the temperature of 
the electric furnace, which is possible in the ordinary arc furnace when 
run as a resistance furnace, it has been found possible to make ferro¬ 
manganese without an excessive loss of manganese by volatilization. 


a Moissan, H. The electric furnace. Translated by V. Lenhcr, 1904. 




PRESENT STATUS OF MANUFACTURE OF FERRO-ALLOYS. 105 


This ferromanganese is usually combined while molten with molten 
ferrosilicon to produce silicomanganese, or a similar alloy. 

There has been comparatively little change in the type of electric 
iurnace used for making ferro-alloys since 1899. In many plants the 
old carbide furnaces are still in operation, and where the ferro-alloy 
is simply being produced directly from the ore 'with carbon as a reduc¬ 
ing agent, the furnace is essentially of the old Siemens crucible type, 
having a conducting hearth of carbon and an upper vertical electrode 
(fig. 38). There are several modifications, which are described later, 
but their difference in design is mainly in shape and in the manner of 
introducing the current. With one or two exceptions, introduced 
lately, ferro-alloy furnaces are run with open tops, as in the first years 
of manufacture. There is no shaft, so that most of the reduction is 
by solid carbon. 

PRESENT STATUS OF THE MANUFACTURE OF FERRO¬ 
ALLOYS IN THE ELECTRIC FURNACE. 

The growth of the ferro-alloy industry in Europe has been rapid 
since 1899, but comparatively slow in the United States. In Europe 
there are about 25 plants engaged in the manufacture of ferro-alloys 
by the electric furnace, as compared with two plants in the United 
States. In addition to these there are three companies using means 
other than the electric furnace in the United States, and one electric- 
furnace ferrosilicon plant in Canada. 

There are several reasons why the growth has been slower in Amer¬ 
ica than in Europe. Hydroelectric power is not as cheap here and not 
so favorably located for the receipt of raw material and the sale of the 
product. The water-power sites can not be developed so cheaply as 
many of the foreign sites, where the cost per kilowatt-year varies from 
$10 to $20, as compared with $20 to $40 in the United States. In 
Canada power is somewhat cheaper, but much of it is in inaccessible 
places. Most of the Norwegian and Swedish plants are on tidewater 
or navigable rivers. French works are within about 200 miles of 
Marseilles. The use of ferro-alloys in the manufacture of high-class 
steels did not advance as rapidly in the United States as in Europe. 
And owing to less favorable natural advantages, electrochemical and 
electrometallurgical industries in general have not made so rapid 
progress and growth. 

A large proportion of the ferro-alloys used in the United States is 
imported, as, although there is a duty, local manufacturers are not 
able to supply the whole demand. About one-half of the ferro¬ 
manganese and one-half of the ferrosilicon, as well as a large part of 
the ferrotungsten, used in the United States is imported. More 
ferrotitanium and ferrovanadium is manufactured here than abroad. 
The ferrochrome production just about supplies the domestic demand. 


106 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 



In Europe the industry of manufacturing ferro-alloys in the electric 
furnace is in excellent condition commercially, with the demand for 
alloys steadily increasing. Because of the race between European 
countries in the building of large navies, there is a great demand for 
ferrochrome. In Europe, the sale of ferro-alloys, especially ferrosilicon 
and ferrochrome, is controlled by a syndicate of the various plants, 

each plant, according to its capacity, 
supplying a certain part of the total 
market demand. 

In the United States there is a ferro- 
titanium manufacturing company at 
Niagara Falls, N. Y. An electrometal¬ 
lurgical company has one plant at Ka¬ 
nawha Falls, W. Va., where the principal 
product is ferrochrome, and another at 
Niagara Falls, N. Y. Other alloys made 
are ferrosilicon, ferrotungsten, ferrova- 
nadium, ferromolybdenum, and ferro- 
phosphorus. A chemical company at 
Primos, Pa., manufactures metals and 
ferro-alloys by chemical methods or in 
combustion furnaces. Among its prod¬ 
ucts are ferrotungsten, ferrovanadium, 
tungsten metal, ferromolybdenum, fer¬ 
rochrome, ferronickel, and ferroboron. 
Another company manufactures ferro¬ 
vanadium by the thermit process at 
Bridgewater, Pa. Another company has 



figure 38.— Plan and elevation of sie- a plant for the manufacture of metals 
mens type of ferrosilicon furnace. ^ ferro _ a l loys at Newark, N. J., blit 

imports most of its products from its foreign works. Among its prod¬ 
ucts are ferrotitanium, ferrovanadium, ferromolybdenum, ferrochro- 
mium, and chromium. 


TYPES OF ELECTRIC FURNACES USED IN FERRO-ALLOY 

MANUFACTURE. 


FERROSILICON FURNACE OF THE SIEMENS TYPE. 

A furnace commonly used in the manufacture of ferrosilicon and 
other ferro-alloys is of the Siemens type. (Fig. 38.) The furnace is 
circular in cross section with one upper carbon electrode and a con¬ 
ducting hearth of carbon. The electrodes are held by holders of 
various types, some of which are shown in figure 39 and in figures 17 
to 35. The holders are attached to cables running to hand adjust¬ 
ment wheels. The electrode holders are not usually water cooled. 












































ELECTRIC FURNACES IN FERRO-ALLOY MANUFACTURE. 107 


As yet the use of round electrodes threaded for continuous feeding 
has not been widespread in ferro-alloy works. In the ferrosilicon 
furnace it is necessary to line the bottom with carbon paste resting 
on an iron plate to which the bottom electrical connection is made. 
The paste of carbon may be surrounded by fire bricks, which are set 
in a steel shell or are held together by sheet-iron bands. The fire 
bricks are often not used at all. There is one tap hole. Fire brick 
can not be used as the interior lining in a ferrosilicon furnace, because 
it is rapidly attacked by the ferrosilicon. The older furnaces are 
operated with single-phase alternating current, but the more recent 
installations are connected to a phase of a three-phase circuit as shown 
in the lower view of figure 50. These furnaces are built in sizes vary- 



1 


o o o 





O O O 




Figure 39.—Electrodes and holders used in Siemens type of ferrosilicon furnace. 


ing from 200 to 1,000 kilowatts. A 225-kilowatt furnace may have a 
crucible 2 feet 6 inches in diameter at the top and about 2 feet in 
diameter at the bottom. The external dimensions are: Diameter, 4 
feet; height from base to top, 5 feet; masonry base, about 1 foot 3 
inches high. The lining is about 9 inches thick. The furnaces are 
operated at 50 to 80 volts. A 12-inch square or circular electrode is 
used. The power factor varies from 0.8 to 0.9. 

If a ferrochrome or alloy of medium carbon percentage other than 
ferrosilicon is to be made in a furnace of this type, the carbon 
bottom is used, but in the walls the carbon is replaced by a basic 
lining of magnesite and tar. After a furnace has been operating 
some time, the material of the charge chills on the walls forming its 
own lining, and some of the ferro-alloy reduced tends to freeze on the 
hearth, thus protecting the main part of the molten metal from the 

























































108 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


carbon. If a ferrochrome containing loss than 2 per cent carbon is 
desired, the lining is of chromite, but this is rather expensive. Ferro- 
silicon and ferrochrome furnaces of this type have been in continuous 
operation for periods of two to four years. 

Usually the smaller furnaces are charged by a laborer, who shovels 
the new materials from the floor at the tapping level into the top of 
the furnace. Larger furnaces have a steel platform around the top 
for charging from a bin system. In some works the furnaces are set 
on trucks, so that an old one may be quickly replaced by a new one. 



KELLER FURNACE. 

The Keller furnace (fig. 40), used for the manufacture of calcium 
carbide and ferro-alloys, consists of two iron casings of square cross 
section, forming two shafts that connect with each other at the lower 
end by means of a lateral canal. There are two vertical carbon 
electrodes connected in series with the slag and the metal. Ordi¬ 
narily the current flows through the electrode in one shaft through 
the charge and through the other electrode, but when the furnace is 
being started after repairs the connection between the electrodes is 



















































ELECTRIC FURNACES IN FERRO-ALLOY MANUFACTURE. 109 

made by carbon blocks at the base of each shaft, which are connected 
by copper bars. There are two tap holes, one in each shaft. The 
lining used depends on the alloy being made. The electrodes are 
built of carbon blocks to a total cross section 30 inches square, and 
are not designed for continuous feeding. They are 4 to 5 feet long. 
The furnaces are about 14 feet long, 7 feet high, and 6 feet wide. 
Extra electrodes are kept ready to replace worn ones. Adjustment 
of electrodes is by hand. 

The Keller furnace is built in sizes using 900 to 2,200 kilowatts. 
Some furnaces are connected as shown in the lower view of figure 50 
and others are directly 
connected to a single¬ 
phase system. The fur¬ 
naces are operated at 50 
to 70 volts. The power 
factor is about 0.7 to 08. 

CHAPLET FURNACE. 

The Chaplet furnace 
(fig. 41) for ferro-alloy 
manufacture has two 
electrodes in series, one 
of which is in one cham¬ 
ber, the other being on 
a channel extending from 
the main smelting cham¬ 
ber. The current passes 
through a vertical carbon 
electrode, through the 
bath and channel to the 
other vertical electrode. 

The Chaplet furnace 
has been used by one 
company especially in 
the manufacture of low- 
carbon ferro-alloys. In making low-carbon alloys it is usually operated 
with a roof when refining, but when reducing directly to a high- 
carbon alloy the roof is removed. The lining is of dolomite, magne¬ 
site or chromite, with a silica-brick roof. The furnace has been built 
in sizes of 120 to 150 kilowatts. 

GIROD RESISTANCE CRUCIBLE FURNACE. 

In its early experiment work the Girod Co. devised a crucible fur¬ 
nace in which heating is by resistance. This furnace (fig. 42) con¬ 
sists of a crucible of some refractory material, which is surrounded 









































































110 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


by a material of high electrical resistance. The use of ferrosilicon for 
this purpose was patented by Girod. Sometimes coke is mixed 

with the ferrosilicon to form the resistor. 
Outside of the resistor are set four carbon 
blocks, which serve as electrodes and are 
separated by brick of high insulating quali¬ 
ties to prevent short circuits. The whole is 
incased in a steel shell and mounted on a 
framework for tilting by hand. The mate¬ 
rials are charged in by hand, and the cruci¬ 
ble is covered with a brick cover. Either 
direct or single-phase current may be used. 
A general difficulty with a furnace of this 
type is the prevention of short circuits 
caused by uneven heating of the crucible, 
and care must be taken to connect the fur¬ 
nace so that the current takes the longest 
possible course. The furnace is used for 
manufacturing ferro-alloys that do not re¬ 
quire a tempera- 



k'-' J 
8 


< 


"V M 

*"X 

; 

s 

S 

5 




V: 


S „ ' 


✓. 

:<• 
' s 

N-r-j 






Figure 42.— Plan and elevation of 
Girod resistance furnace. 


ture above 1,600° 
C. It is built in 
sizes up to 150 
kilowatts. 



GIROD ARC FURNACE. 

For the manufacture of ferro-alloys of 
high reducing or melting point, other than 
ferrosilicon, Girod uses a furnace (fig. 43) 
of circular cross section, with one or more 
upper carbon electrodes in parallel and a 
conducting hearth of dolomite and tar 
having mild-steel rods embedded or open¬ 
ings into which molten metal is poured and 
allowed to freeze. These rods are placed 
radially around the bottom. The ends pro¬ 
ject outside and are water-cooled where the 
cables are attached. The lining is usually 
of dolomite or magnesite throughout, but 
with the production of low-carbon ferro- 
chrome a chromite lining may be used. 

Where there are several upper electrodes the 
diameter of the furnace is greater and the 
depth about the same as in the single elec¬ 
trode furnace. The general dimensions are 

about the same as given for the Siemen’s furnace, with a conducting 
hearth of carbon. Either direct or alternating current may be used. 



Figure 43.—Plan and elevation of 
Girod electrode ferro-alloy furnace. 





























ELECTRIC FURNACES IN FERRO-ALLOY MANUFACTURE. Ill 

MERAKER FURNACE. 


/, v v V. ''//*//’//‘ 

' / /////s /, ///, / /, '////,/. V. V, V, v, v 


✓ ' 
* 


,. // 


* v , . , I , . . , , i , 

, "/ '/ '/ '/ V '/ '/ '/ '/ '/ '/ '/ 

'' '' '' '/'S'/'/'.''/'. 


'/ 

// 


At Kopperaaen, near Meraker, Norway, a furnace (fig. 44) 
similar to the Alby carbide furnace is being used in the production of 
ferro-alloys, especially ferro- 
chrome. This furnace is rectan¬ 
gular in cross section, with an 
upper rectangular carbon elec¬ 
trode, and a conducting bottom 
of carbon, forming the other 
electrode. The carbon bottom 
rests on a concrete foundation 
or the whole furnace may be set 
on wheels so as to be movable. 

The lining consists of magnesite 
and tar, 9 inches thick. The 
whole is incased in a f-inch steel 
shell. In one end of the furnace 
there is a tap hole. At the oppo¬ 
site end connection is made to 
the bottom electrode. The upper 
electrode consists of four carbon blocks 10 by 12 inches by 6 feet long, 
set side by side so as to make an electrode 10 by 48 inches in section. 



Figure 44.—Plan and elevation of ferroclirome 
furnace at Kopperaaen, Norway. 



The whole electrode is covered with sheet iron in an endeavor to 
reduce oxidation and is held by the holder shown in figure 45 (right- 





























































































































































































112 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


hand view), which is supported by cables from above. A spare elec¬ 
trode is left hanging from the framework above the furnace ready to 
replace one worn out. 

A 750-kilowatt furnace is about 10 by 6 feet in section outside at the 
top and about 9 feet by 5 feet 6 inches at the boitom. The internal 




depth is about 5 feet. The car¬ 
bon block at the bottom is 1 foot 
thick and rests on a concrete 
foundation 1 foot above the floor. 
The furnace top is about 7 feet 
above the floor. These furnaces 
are operated at 65 volts with 
either direct or alternating cur¬ 
rent. 

A furnace of this design with 
a closed top has been designed 
at Kopperaaen. This consists 
chiefly of a steel hood l\ feet 
high, lined with fire brick. 
There is an opening for the elec¬ 
trode, flues for drawing off the 
gases, and charging doors. Lit¬ 
tle gas escapes from this furnace 
except through the flues. The 
top reduces the electrode con¬ 
sumption considerably. 

SERIES FURNACE. 

A furnace designed to avoid 
the use of a conducting hearth 
and commonly called the 
^ series ” furnace, is shown in 
figure 46. The furnace shown 
has two vertical carbon elec¬ 
trodes connected in series for 


Figure 46.—Plan and elevation of single-phase series operation With sillgle-phase CUr- 
ferro-alloy furnace. , TJ . ,, , ® 1 

rent, it three-phase current is 
used there are three electrodes connected each to a phase of the 
system in the delta connection. The construction of the furnace 
proper is in general the same as for furnaces already described, 
except that there is no electrical connection with the hearth. 
Furnaces of this type have been built in sizes up to 3,000 kilowatts. 

Three-phase furnaces may be of the shape shown in figure 46, with 
three electrodes arranged in a triangle and each connected to a phase 































































































ELECTRIC FURNACES IN FERRO-ALLOY MANUFACTURE. 113 

ol ft three-phase system. Or the furnace may be rectangular, as 
shown in figure 47. In neither form is there electrical connection to 
the bottom. A furnace of this type has been built to take 5,000 
kilowatts. 

HELFENSTEIN FURNACE. 

A furnace recently designed for the manufacture of calcium carbide 
and ferrosilicon on a large scale is the Helfenstein furnace (fig. 48), 
which has several shafts set side by side feeding a crucible beneath. 
Each shaft has its own vertical top electrode, but all are connected 
electrically by bottom electrodes in the form of a conducting bottom 
common to all the shafts. 0 There is no other connection between the 
shafts, so that it is possible to produce different products simultane- 



Figure 47.—Elevations of three-phase series ferro-alloy furnace. 


ously. As shown in figure 48, the shafts enter the crucibles from each 
side, with the electrodes in the center. The whole furnace is thus 
rendered air tight. One large 7,500-kilowatt Helfenstein furnace is 
operating in France and several are being constructed. The use of 
large units with an air-tight furnace reduces the electrode and the 
power consumption considerably. 

GENERAL CONSTRUCTION OF ELECTRIC FERRO-ALLOY FURNACES. 

FUNDAMENTAL PARTS. 

From the types of electric furnaces described it may be seen that 
in general an electric furnace for ferro-alloy manufacture consists of 
a crucible without a roof, having either a conducting or nonconduct- 


a Taussig, R., Present status of the development of large electric furnace: Met. and Chem. Eng. vol. 10, 
1912, p. 686. 

























































































114 the electric furnace in metallurgical work 



Figure 48.—Elevation of Helfenstein furnace. 



Figure 49.—System of electrical connections for several small furnaces. 






































































































































































ELECTRIC FURNACES IN FERRO-ALLOY MANUFACTURE. 115 

ing hearth and an upper vertical carbon electrode or electrodes. 
Most of the furnaces first built had a conducting hearth, and this is 
still common in furnaces up to about 750 kilowatts, but for larger 
sizes experience has shown that the nonconducting hearth is prefer¬ 
able. There is a considerable loss of electrical energy by dissipation 
through the lining, and there is a tendency to have a lower power 
factor because of the circuit being more completely inclosed in iron. 
In working a small furnace intermittently—that is, discharging it 
completely before charging it again—the conducting-hearth furnace 
is much more easily operated and started when cold. When a large 
furnace is to be operated continuously for several months at a time 
on one alloy, this advantage of the conducting hearth is of no impor¬ 
tance. A factor little considered in the construction of ferro-alloy 
furnace is the power factor. Most of the furnaces are completely 
inclosed in sheet steel, whereas bands would do as well, with much 
less induction in the circuit. 

CONSTRUCTION AND LIFE OF LININGS. 

As has been stated, the ferrosilicon furnaces are lined with carbon, 
and most of the furnaces to be used in producing other alloys with a 
basic lining of magnesite or dolomite brick or a mixture of tar with 
either material. When low-carbon ferrochrome is being made, the 
lining in some furnaces is chromite. Generally a furnace is designed 
so that the electrode or electrodes are at a sufficient distance from 
the walls to permit a chilling of the material charged upon the walls. 
This practice has given the most satisfactory lining. With such an 
arrangement furnaces have been run two to three years without being 
relined. The average furnace operating continuously runs about two 
years before being shut down for repairs. A furnace being operated 
intermittently must of course be relined oftener. 

ELECTRODE HOLDERS. 

TYPES. 

There are two general types of electrode holders used—first, one 
with two clamps bolted around the electrode, leaving the top of the 
electrode exposed; and second, one that grips from above, making it 
impossible to add a section of electrode from above. The former type 
has been commonly used in electric steel furnaces., but does not seem 
to have been so widely used in ferro-alloy manufacture. This is 
probably because, with the lack until rather recently of an amphorous- 
carbon electrode threaded for continuous feeding, the most convenient 
mode of suspension has been by chain with the second type, rather 
than by a lateral steel frame, as is necessary in the first type. In the 
future the use of the first type of holder will probably increase because 


116 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

of the possibility of reducing the electrode consumption by using up 
all butts. A method formerly sometimes used for joining electrodes 
is shown in figure 39. This connection was not entirely satisfactory 
and was not widely adopted. 

Various designs of the second type are shown in figure 39. Above 
the point where it grips the electrode the holder is attached to a chain 
or cable, by means of which it is supported. With a holder of this 
type about one-third of the electrode is not used. Electrical con¬ 
nection is made by cables attached to the holder. 

In figure 45 is shown a type of electrode used in Norway and 
Sweden for rectangular furnaces. It consists of carbon blocks held 
together in a framework of steel by wedges, the electrical connec¬ 
tions being made by cables attached to the holder itself. The whole 
is suspended by cables. In figure 45 (left-hand view) is also shown 
an Italian method, in which the electrical contact is made against 
the end of the electrode instead of on the sides for the purpose of 
getting a more even distribution of current throughout the electrode. 
It is water cooled and the most perfect design technically, but practi¬ 
cally is not very widely used. 

In many plants, before any of these holders are connected, each 
electrode is covered with sheet iron to reduce the electrode consump¬ 
tion by oxidation. At some works it is stated that it is doubtful 
whether this practice results in enough saving to warrant the addi¬ 
tional expense. The built-up electrodes are set in a cement of tar 
and carbon to fill the cracks. 

Great care must be taken in building up the electrodes or there 
will be excessive local heating. 

WASTE OF HEAT IN OPEN-TOP FURNACES. 

As most of the reduction of oxides in ferro-alloy manufacture is 
done by solid carbon at a high temperature, most furnaces are run 
with an open top into which the charge is placed, around the elec¬ 
trode. There results a considerable waste of heat that might be 
used in preheating the charge. In most of these furnaces the elec¬ 
trode dips about 12 to 15 inches beneath the top of the furnace, 
which is kept filled with cold material so that the molten mass be¬ 
neath will not be exposed. There is burning of carbon monoxide 
around the electrode and an escape of a large volume of gas through 
the top of the furnace house. As previously mentioned, there has 
been a seemingly successful attempt made to overcome this waste at 
Kopperaaen, Norway, with a modification of an existing furnace. 
The Helfenstein furnace has this objection removed as it is air-tight, 
and in addition has feeding shafts, where the charge is preheated by 
the waste gases. In the manufacture of the higher-priced alloys, 
such as ferrotungsten and ferrovanadium, it is impossible to use any 


ELECTRIC FURNACES IN FERRO-ALLOY MANUFACTURE. 117 


furnace but one with an open top because of the intermittent nature 
of the operation, but in making ferrosilicon and ferrochrome, it seems 
advisable to preheat the charge as much as possible. 

CHARACTER OF ELECTRIC CURRENT. 

A large number of the first ferro-alloy furnaces were supplied with 
direct current when the furnace house was built adjoining the power 
house so that there was only about 20 feet between the furnace and 
the generator. It was soon found that the electrolytic action in a 
direct-current furnace resulted in deposition of potassium, sodium, 
calcium, aluminum, and other metals with the alloy so that as pure 
a product could not be obtained with direct as with alternating cur¬ 
rent. When alternating current was first used, single-phase current 
was more common, so that the 
arrangement remained the same as 
previously, the generator deliver¬ 
ing directly to the furnace at the 
desired voltage without any trans¬ 
formation. 

Later when three-phase current 
became common, furnaces designed 
to take single-phase current were 
connected in groups to three-phase 
systems by several methods. A 
method commonly used for the fur¬ 
nace with a conducting hearth and 
one or more vertical electrodes is 
shown in figure 49 (p. 114). The 
primary and secondary are both connected in star connection, with the 
furnace bottom as the neutral point of the secondary circuit. There 
are two transformers to a phase, supplying two furnaces. In this 
system there is apt to be an unbalancing of the load on the three 
phases. It is used only with small furnaces. To get a better bal¬ 
ancing of phases, conducting-hearth furnaces are connected as shown 
in figure 49, where each furnace is connected to a phase or there 
may be two furnaces to a phase, the whole system being in delta 
connection. 

For single-phase furnaces the method shown in figure 50 is the 
best, where three nonconducting bottom furnaces are each connected 
by the delta arrangement to the three transformers of a three-phase 
line. Thus the primary and secondary are both connected by the 
delta system. By this arrangement there is a better balancing of 
the load in the separate phases. Also it is possible to cut out one 
furnace if desired. 



Figure 50.—Delta connections of three single¬ 
phase furnaces. 

































































118 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


A three-phase furnace with a nonconducting bottom is connected 
as in figure 51, where three electrodes are each connected to a trans¬ 
former, there being a common neutral line between the three trans¬ 
formers. It is not difficult to keep the phases balanced in this sys¬ 
tem, and it is very satisfactory. If there is more than one electrode 
to a phase in a furnace of this type it has been found difficult to 
keep the phases balanced. That has been the experience with one 
electric pig-iron furnace, whereas with others no difficulty has been 
experienced. 

SOME EUROPEAN ELECTRIC-FURNACE FERRO-ALLOY 

PLANTS. 

KELLER, LELEUX & CO., LIVET, I SERE, FRANCE. 

The main works of Keller, Leleux & Co. are at Livet, Isere, France, 
about 20 miles from Grenoble. There is also a small plant using 

450 kilowatts at Kerrouse, in the 
same district. The company orig¬ 
inally manufactured only calcium 
carbide, but later took up ferro¬ 
alloy production on a large scale 
in conjunction with the production 
of carbide. Livet is connected with 
Grenoble, which is on the main line 
of the Paris, Lyons & Marseille 
Railroad, by an electric and steam 
tramway. 

POWER SUPPLY. 

The company develops its own 
power on the Romanche River, 
where a head of 200 feet is utilized 
by means of a 1 J-mile tunnel. The 
cost of power is said to be $10.66 to $13.33 per kilowatt-year, or 
0.12 to 0.15 cent per kilowatt-hour. At high water there is a maxi¬ 
mum of 12,000 to 14,000 kilowatts available, but for the four months 
from November 1 to March 1 this drops to 7,000 kilowatts, some of the 
furnaces being shut down and others operated with reduced power. 

The first installation of generating machinery, which is still in use, 
consists of six single-phase dynamos of 900 kilowatts each, delivering 
current of 55 cycles directly to six furnaces at 55 volts. A more 
recent installation contains three 2,200-kilow r att three-phase machines, 
connected in parallel and generating current at 2,300 volts and 25 
cycles. This is stepped down by transformers at the furnaces. In 
addition to the equipment mentioned there are several smaller 
generators used for general purposes. 



Figure 51.—Electrical connections of a three- 
phase furnace. 































EUROPEAN ELECTRIC-FURNACE FERRO-ALLOY PLANTS. 119 
GENERAL PLAN OF THE WORKS AND FURNACES. 

The plant is arranged so as to require considerable rehandling of 
materials to be charged into the furnaces. There are 3 furnace 
houses of stone-and-steel construction, 35 feet wide, 75 feet long, and 
about 20 feet high. Each building contains three furnaces, which 
are set up against one wall with the transformers in a room directly 
outside the wall. Or, if the furnaces are supplied directly by the gener¬ 
ators, the arrangement is the same except that there are no trans¬ 
formers. The space in front of the furnaces is used as a tapping 
floor. Both carbide and ferro-alloy are tapped into small ladle 
trucks and dumped in an adjoining shed for cooling and packing. 
Around the top of each furnace there is a steel floor for charging. 

There are six Keller furnaces of the t}q>e previously described (fig. 
40), working on ferro-alloys and three on calcium carbide. The car¬ 
bide furnaces take from 1,200 to 2,200 kilowatts each, while the ferro¬ 
alloy furnaces are from 900 to 1,000 kilowatts capacity, making a 
total of about 6,000 kilowatts being used in ferro-alloy production. 
The furnaces directly connected to the single-phase generators 
receive current at 50 volts at the furnace. The furnaces on the three- 
phase circuit have a single-phase transformer to each furnace as 
shown in figure 50, so that the voltage varies from 50 to 70 volts at 
the furnace.. , 

PRODUCTS. 

Three grades of ferrosilicon, containing 25, 50, and 75 per cent 
silicon, are manufactured at these works. The charge consists of 
iron turnings, quartzite, and anthracite coal. Only iron turnings 
containing less than 0.10 per cent phosphorus are used to obtain the 
iron. The cost of turnings at Livet is about $14 per ton. The 
quartzite is ground and contains 94 to 96 per cent Si0 2 , with some 
phosphorus. Sand is not used to supply the silicon at this plant as it 
appears to cause irregular operation of the furnaces. For a reducing 
agent, anthracite coal containing 7 per cent ash, 0.013 per cent 
phosphorus, and 0.41 per cent sulphur is used. The materials are 
weighed and throughly mixed before being charged. About 500 
pounds of 30 per cent alloy is tapped every 2 hours. The 30 per 
cent ferrosilicon requires 3,500 kilowatt-hours per ton, and the 50 
per cent alloy 6,800 kilowatt-hours per ton. After the slag has been 
tapped into a truck ladle it is skimmed from the metal by means of a 
preen log placed crosswise on a wooden handle. The molds are lined 
with sand. After having been allowed to cool the ferrosilicon is 
broken up with a hammer and packed into wooden kegs. 

Ferrochrome of all grades is manufactured at Livet. The raw 
materials used consist of chromite ore containing 35 to 40 per cent 
chromium, with traces of phosphorus and sulphur, and anthracite 
coal as a reducing material. 


44713°—Bull. 77—16-9 



120 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

Other ferro-alloys made are silicomanganese, ferrotungsten, ferro- 
titanium, and ferrovanadium. The total yearly production of the 
Keller works consists of about 1,500 tons of 25 to 30 per cent ferio- 
silicon, 3,000 tons of 50 per cent ferrosilicon, 6,000 tons of ferro- 
chrome, 1,500 tons of silicomanganese, 6,000 tons of calcium carbide, 
and smaller quantities of the higher priced ferro-alloys. 

SOCIE TE ELECTRO-METALLURGIQUE PROCEDES PAUL GIROD, 

UGINE, SAVOIE, FRANCE. 

In 1898, Girod began the experimental work on the manufacture 
of ferro-alloys in the electric furnace at Albertville, Savoie, France, 
with a small 20-kilowatt furnace. In 1899 he opened at Albertville 
a small works of 38-kilowatt capacity. Later in the same year the 
erection of a larger plant was begun at that place. The Albertville 
plant had a capacity of 750 to 950 kilowatts, and consisted of 5 
furnaces, each taking 150 to 200 kilowatts. The plant has since been 
dismantled and the equipment moved to Ugine. 

In 1903, the construction of new works was begun at Courtepin, 
Switzerland. The plant uses 2,250 kilowatts of 25-cycle three-phase 
current, which is delivered at 32,000 volts and stepped down to 50 
to 75 volts at the works. The furnaces at Courtepin are used almost 
entirely in the production of ferrosilicon containing 25 to 30 per cent, 
50 per cent, 75 per cent, and 95 per cent silicon. 

In June, 1903, the present company was organized with a capitali¬ 
zation of $360,000, which has been increased tq $2,400,000, of which 
$1,000,000 is in bonds. In 1903 the works at Ugine were erected. 
In addition to the works mentioned, there is a power plant at St. 
Gervais, Switzerland. 

Ugine is situated on a branch line of the Paris, Lyon & Mar¬ 
seille Kail way between Annecy and Albertville. The works are 
about three-quarters of a mile from the main line, with which con¬ 
nection is made by an electric tramway for freight haulage, which 
is operated by the Girod Co. The buildings are all on the north 
bank of the Arly Kiver. 

POWER SUPPLY. 

The total capacity of all of the Girod power plants is about 28,000 
kilowatts. There is a possible development of 30,000 kilowatts 
more, a total of 58,000 kilowatts. The average cost of power from 
all sources is about $18.66 per kilowatt-year, or 0.21 cent per kilo¬ 
watt-hour. 

A short distance up the Arly Kiver from the plant is the dam 
of one of the power plants of the Girod Co. The water is led 
directly to the plant by a pipe line, the total fall being 416 feet. Ten 
dynamos, driven by 10 Pelton wheels, generate 6,000 to 7,000 kilo¬ 
watts of single-phase current, which is conducted directly to the 
furnaces in the old furnace house. 


EUROPEAN ELECTRIC-FURNACE FERRO-ALLOY PLANTS. 121 

At La Fayet, also on tlie Arly River, at a considerable distance 
from Ugine, 9,000 to 15,000 kilowatts of three-phase current is 
developed. This is transformed at the works from 45,000 to 50 or 
75 volts for the furnaces and 2,500 volts for conversion to direct 
current. About 4,500 kilowatts of three-phase current is obtained 
from a plant at St. Gervais, Switzerland, on the Bonnart River. To 
supply a deficiency during the low-water months, from October 1 to 
April 1 , 6,000 to 7,500 kilowatts, all three-phase at 4,500 volts, is 
leased from another electrometallurgical company at Veuthin. 

The present capacity of the two Girod power plants on the Arly 
River that supply the Ugine plant is about 24,000 kilowatts. For 



Figure 52.—Flan of Girod ferro-alloy plant: l, garage;-2, villa; 3, porter’s lodge; 4, dwelling house; 5, 
portal; G, dwelling house; 7, road; 8, fitting and tinsmith shop, 75 by 25 feet; 9, metal-sorting shop, 75 by 25 
feet; 10, laborers’ dining hall; 11, raw-materials storeroom, 285 by 40 feet: 12, workshop, GO by 40 feet; 13, 
dining room; 14, lavatories; 15, foremen’s office; 10, packing shop, 60 by 40 feet: 17, hammer with falling 
weight of 220 pounds; 18, foremen’s office; 19, shop for fitting up electrodes; 20, repairing shop; 21, work¬ 
shop for preparation of graphite; 22, general office; 23, transformer house, 175 by 25 feet; 24, furnace house, 
160 by 25 feet; 25, covered yard, 160 by 25 feet; 26, furnace house, 160 by 25 feet; 27, transformer house, 1G0 
by 25 feet; 28, ferro-alloys store house, 130 by 50 feet; 29, covered yard, 440 by 30 feet; 30, old furnace house, 
440 by 30 feet; 31, power house, 360 by 40 feet; 32, stock shed, 360 by 50 feet; 33, raw-materials storehouse; 
now smelting works, 520 by 75 feet; 34, Arly River; 35, conduit pipe; 36, chimney, 125 feet high; 37, road to 
Ugine; 38, graphite and carbon storehouse, 150 by 100 feet; 39, chimney; 40, electrode storehouse, 170by 
40 feet; 41, furnace house for electrode manufacture, 170 by 40 feet; 42, electrode presses, etc., 110 by 75 feet; 
43, sawmill; 44, graphite storehouse; 45, dwelling house. 

four months, from October to February, and sometimes to April, 
the current delivered is reduced to about 12,000 kilowatts when leased 
power is used. All of the power developed by the Girod plants, 
except about 6,000 kilowatts that supplies the electric steel works, is 
used in ferro-alloy manufacture. 

GENERAL PLAN OF THE WORKS. 

The works cover about 500,000 square feet, including the electrode 
department, which is operated in conjunction with the ferro-alloy 
plant. The general layout of the plant is shown in figure 52. 

The old furnace building is of stone construction, 440 feet long, 
30 feet wide, and 18 feet high. The power house runs parallel to it. 























122 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

with a wall between the furnaces and the generators, so that a 
furnace is not more than 20 feet from its generator. The ends of 
the furnace building are open, with an open ventilation on the top 
for the length of the building. Adjoining the furnace building on the 
side away from the furnaces is an open shed into which the finished 
products are dumped to cool. Ore, sand, and coal are weighed and 
mixed on the floor, from which they are shoveled into the furnace 
tops. 

The furnaces in the old works are chiefly used for the manufacture 
of the higher-priced alloys. There are 18 furnaces, ranging in size 
from 150 to 560 kilowatts capacity each. Both crucible and elec¬ 
trode furnaces are installed. The furnaces, about 6 feet apart, are 
set along one wall, with the wheel for hand regulation of electrodes, 
as well as the electrical instruments, on the opposite wall. The 
electrodes are suspended by cables running over blocks on the steel 
trusses of the roof. 

At the new Works the raw materials are unloaded from the rail¬ 
way cars into the open raw-material shed. An electromagnet crane 
is used in unloading iron turnings. The ores are then carried in 
small electrically hauled cars to the new furnace house, where they 
are elevated to bins above the furnaces. Weighing, mixing, and 
charging are done here from a floor at the level of the furnace top, 
considerable labor being thus saved over that necessary at the old 
plant. The transformers for the three-phase current are set in 
rooms parallel to each furnace house. The furnaces are set close to 
the dividing wall. Beyond the other wall of the furnace house 
is an open shed, into which the hot products are dumped. The 
furnaces in the new works are all of the electrode type, taking 375 to 
900 kilowatts. The electrodes are supported by cables running to 
the steel framework over the furnaces. Regulation is by hand, as in 
most ferro-alloy furnaces. 

PRODUCTION. 

The Girod Co. employs 400 to 500 men in the production of 
ferro-alloys, the yearly value of which is between $2,000,000 and 
$3,000,000. The quantity produced varies considerably from year 
to year, but the production is estimated at 15,000 to 20,000 tons; 
ferrosilicon, 30 to 90 per cent silicon, 6,000 tons; ferroclirome, 5,000 
tons; ferrotungsten, 1,000 tons; silicomanganese, 2,000 tons; other 
alloys, 1,000 tons. The details of manufacture of these alloys is 
about as is later described in general under each ferro-alloy. 

MERAKER ELECTRIC SMELTING CO. 

The works of the Meraker Electric Smelting Co. are at Kopperaaen, 
Norway, 55 miles east of Trondjhem on the main line of the railroad 
to Stockholm. The company operates an electric-furnace plant for 


EUROPEAN ELECTRIC-FURNACE FERRO-ALLOY PLANTS. 123 

*> 

the manufacture of calcium carbide and ferro-alloys at Kopperaaen, 
and a pulp-grinding plant about 3 miles west, at Meraker. The con¬ 
cern has been manufacturing since 1905, and, in spite of several fires 
that almost destroyed the plant, has been very successful. In the 
summer of 1912, ferrochrome was the only alloy manufactured, 
but it was the intention of the company to begin the production of 
other ferro-alloys, especially ferrotitanium, during the next year. 

POWER SUPPLY. 

9 

The company owns its own power plants. At Kopperaaen there 
is a fall of 250 feet in the Kopperaaen River. The river is fed by two 
lakes regulated so as to give a minimum flow of 160 cubic feet per 
second and a maximum flow of 210 cubic feet per second. At present 
about 2,250 kilowatts is developed at the foot of this fall at Kopper¬ 
aaen, and 750 kilowatts more is received from the power plant at the 
pulp mill in Meraker. The total power used in the electric-furnace 
plant is about 3,000 kilowatts. At Kopperaaen there are two 1,125- 
kilowatt direct-current generators delivering current at the furnaces 
at 65 volts and about 14,250 amperes. There are also several small 
units for power and lighting purposes. Of the 3,000 kilowatts now 
being used half is for ferrochrome manufacture and the rest for calcium 
carbide manufacture. The cost of power is stated to be $8.30 per 
kilowatt-year, or 0.095 cent per kilowatt-hour. At a point farther up 
the river 3,000 kilowatts more is to be developed this year, making a 
total of 6,000 kilowatts used in the electric furnaces. When desired 
it is possible to develop 4,000 kilowatts more at this point. 

GENERAL PLAN OF WORKS AND FURNACES. 

Raw materials are unloaded into bins near the Kopperaaen railroad 
station, about one-half mile from and 300 feet above the plant. 
There are bins for coal, limestone, and chromite. Besides the bins 
there is a shipping house where boxes for ferrochrome and iron 
drums for calcium carbide are made. An aerial tramway runs from 
the bins and shipping house to the main storage bins about 200 feet 
from the furnace house but at an elevation 200 feet higher. Here 
the raw materials are dumped from the tram buckets, and boxes and 
drums of product are loaded into the buckets after having been hauled 
up the hill from the furnacehouse by cable skips. At the level there 
is a kiln for calcination of the limestone. From the bins 200 feet 
above the furnace house the ores, coal, and lime are lowered to the 
furnaces by an incline skip discharging into bins above and outside 
the furnace house. 

From these bins the materials are drawn into cars running around 
a floor in the furnace room about 15 feet above the main working 
floor, and are dumped into small chutes at each furnace. The chutes, 


124 


THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


two to each furnace, are about 4 feet deep, and 1^ feet by 1 foot in 
cross section. From these chutes the ore, coal, and lime are drawn 
into small cars and dumped into the furnaces about 15 feet away. 

The furnace house is about 110 feet long, 75 feet wide, and 22 feet 
high, and is built of structural steel with brick-and-stone walls. An 
open ventilator in the roof runs the length of the building. The gases 
from all the furnaces, except one that is covered and connected with 
a stack, escape into the furnace room and pass out through the roof. 

The main floor of the furnace house is cement, with tracks inlaid for 
the hauling of small ladle trucks. There is an open space at one end 
for the dumping of hot carbide and ferrochrome. Around each fur¬ 
nace at the level of the furnace top there is a steel floor, supported 
by iron pillars. The furnaces are charged from those floors, which are 
about 15 b}^ 20 feet. 

There is a steel floor 10 feet wide suspended above the charging 
floor. The main bins are discharged into the individual furnace 
chutes from this floor. This floor also extends out over each furnace 
to make charging of the electrodes less difficult. 

There are five 750-kilowatt furnaces of the Alby type (fig. 44), 
arranged two on each side and one at the end of the room. Only four 
of these arc operated at a time, one being kept in reserve. There is 
also a 450-kilowatt furnace of this arc type with a shallow hearth for 
refining. Three of these furnaces are operated with direct current 
at 60 volts and one by single-phase current at the same voltage. The 
electrode holders are of the type shown in figure 45. A spare one is 
left to facilitate charging at each furnace. Jointed connections for 
continuous feeding are not used. In the four open-top furnaces an 
electrode 48 by 10 inches by 6 feet long lasts about 10 days, whereas 
in tlie covered-top furnace they last 14 to 16 days. The electrodes 
project about 10 to 12 inches into the charge, which is not molten at 
the top, and are consumed down to about 2-foot to 1-foot lengths. 

The lining of magnesite and tar in one ferro-alloy furnace had been 
in use for 22 months and the other 6 months. The power had not 
been off these furnaces at all during that time except for about 15 
minutes a week when electrodes were changed. The current is con¬ 
ducted from the power house at the end of the furnace room by 
copper cables. The connection to the carbon-block base of each 
furnace is made by many small wires leading to the main cable line. 

products: 

The Meraker company produces 4,000 tons of calcium carbide and 
2,000 tons of ferrochrome annually. Turkish ore and English anthra¬ 
cite coal are used for the manufacture of the ferrochrome. In cal¬ 
cium-carbide production the power consumption is about 0.375 kilo¬ 
watt-year per metric ton or 1.5 kilowatt-hours per pound. The power 


FERROBORON. 


125 


consumption for ferrochrome is 0.75 kilowatt-year per metric ton or 
3 kilowatt-hours per pound. The carbide and ferrochrome are tapped 
every 2 and 4 hours, respectively. The carbide is sized before being 
packed into 50-kilogram (110-pound) drums, and the ferrochrome is 
broken into lumps less than 6 inches square and packed into 200- 
kilogram (440-pound) boxes. 

This company makes only ferrochrome that can be produced with¬ 
out the refining process described later, so that the carbon content 
of its product varies from 2 to 10 per cent. It is very easy to make 
a ferrochrome of 5 per cent carbon content without refining the 
product. The cost of manufacture of carbide is given at about $30 
per metric ton. All products are sold through a syndicate of manu¬ 
facturers organized to prevent overproduction if possible. The com¬ 
pany employs 120 men, part of whom work an 8-hour shift and part 
10 hours. The men in the furnace house are on an 8-hour shift. The 
minimum wage is $1.25 for a 10-hour shift. 

FER RO-ALUMINUM. 

Aluminum is usually used by the steel maker in the form of metallic 
aluminum, but sometimes a ferro-aluminum is made. Metallic alu¬ 
minum is supplied in half-round sticks or notched ingots. Ferro- 
aluminum is made containing 5, 10, and 20 per cent aluminum, with 
the rest iron. The other iron-aluminum alloys, such as ferro-alu¬ 
minum silicon, are discussed later. 

The manufacture of ferro-aluminum consists simply in melting 
aluminum and iron together in the desired percentages. This may 
be done in either an electric furnace or a combustion furnace of the 
crucible type. Aluminum or ferro-aluminum is added in the ladle 
and serves only for the deoxidizing of the steel. 

Iron containing 5 to 6 per cent aluminum is fragile.® At 7 per 
cent aluminum the alloy has a crystalline structure. An iron alumi¬ 
num alloy containing over 20 per cent aluminum has no magnetism. 
Ferro-aluminum containing from 0 to 34 per cent aluminum con¬ 
sists of mixed crystal of iron and aluminum. 6 When 34 to 52 per 
cent aluminum is present there are crystals, and with 52 to 100 per 
cent aluminum the alloys FeAl 3 and A1 are found together. 

FERROBORON. 

Ferroboron is not as yet very commonly used, as the effect of boron 
on steel has not been extensively investigated. Ferroboron is manu¬ 
factured directly by the reduction of colemanite Ca 2 B 6 O u , 5H 2 0 and 
iron with carbon in an electric furnace of one of the types already 


aGuillet, L., Etude Industrie! des Alliages Metallique, p. 930. 
b Robin, F., Traitd de Metallographie, 1912, p. 304. 







126 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

described. The analysis of a typical Pacific Coast colemanite is as 
follows : a 

Per cent. 


B 2 0 3 . 27.23 

CaO. 28.80 

HoO. 25.30 

Fe 2 0 3 .Trace. 

Insoluble. 0. 74 


In the western United States there are large deposits of this mineral, 
the principal use for which is in the manufacture of borax. In manu¬ 
facturing ferroboron, carbon is mixed with the colemanite and iron 
turnings or iron ore in sufficient quantity to produce as complete 
reduction as possible, although the slags are usually high in boron. 
The product of the reduction with carbon in the electric furnace is of 
various grades containing 10 to 12, 20 to 25, and 30 to 35 per cent 
boron. A typical ferroboron of the latter class had the following 
composition: 

Per cent. 


Boron. 32. 75 

Carbon. 2. 875 

Sulphur.03 

Phosphorus.005 


In a French patent Girod claims that the presence of boron either 
as colemanite or as the alloy in a charge gives a more fluid slag in the 
manufacture of other ferro-alloys, and if it goes into the alloy increases 
its value. 

Hansen 6 has patented a method for the production of ferroboron 
from colemanite with ferrosilicon as a reducing agent. In this way 
there is no carbon in the ferroboron, but it is apt to contain consider¬ 
able silicon. The colemanite is powdered and briquetted with enough 
ferrosilicon to provide silicon for complete reduction of the boron 
and to slag off the calcium oxide. Water glass or some other suitable 
material is used as a binder. The briquets are subjected to a tempera¬ 
ture of over 2,000° C., giving ferroboron and a calcium silicate slag. 

Ferroboron containing about 10 per cent boron seems to give the 
best results. Ferroboron is added in the ladle and may be used for 
deoxidizing, desulphurizing, and for a fixed addition of boron to steel. 

Guillet c states that the best commercial boron steel is that con¬ 
taining 0.22 per cent carbon and 0.5 per cent boron. Boron steels 
are practically useless unless tempered, when they have high tensile 
strength and elastic limit and great resistance to shock. 


alwai, Iv., and Ballagh, J. L., Investigation of ferroboron: Min. and Sei. Press, vol. 99, 1909, p. 185. 
b U. S. Patent 982135, Jan. 17,1911. 

c Guillet, L., Etude Industrie! des Alliages Metallique, p. 372. 















FERROCHROME. 


127 


FERROCHROME. 

HISTORY. 

More ferrochrome is manufactured in the electric furnace than 
any other ferro-alloy except ferrosilicon. The alloy of iron and 
chromium, called ferrochromium or ferrochrome, has been known 
since 1820 through the studies of Faraday and Stodarts, and also by 
the work of Berthier. Berthier found that by adding ferrochrome 
containing 17 per cent chromium to steel, so as to give 1^ per cent 
chromium in the steel, a product of better quality was obtained. 
Baur found 40 years later that ferrochrome was the best agency to 
use for adding chromium to steel. Other experimental work on 
chrome alloys was done by Fremy, Percy, and Mushet. 

In 1873 Biermann, of Hanover, announced that his firm was pro¬ 
ducing ferrochrome commercially. In 1877 the English firm of 
Hadfield put on the market some ferrochrome containing 10 to 30 
per cent chromium. The French firm of Holtzer & Co. also began 
manufacture. By 1886, as the value of chromium in steel became 
more understood, there were several regular producers of ferrochrome. 
In 1899 there began the production of ferrochrome in the electric 
furnace. Up to that date all of it had been made in either the 
crucible or the blast furnace. 

WORK OF EXPERIMENTERS. 

NEUMANN. 

Neumann a investigated the use of ferrosilicon as a reducing agent 
for chromite (FeO. Cr 2 0 3 ) in the electric furnace in an effort to pro¬ 
duce a carbon-free alloy. The experiments were performed in an 
electric furnace holding about 1 kilogram of charge and operating 
with 100 amperes and 30 to 50 volts. Ferrosilicon containing 91.65 
per cent silicon and 1.03 per cent carbon was used as a reducing agent. 
The chromite contained 31 per cent chromium and 13 per cent iron. 
A mixture of (150Al 2 O 3 + lOOCaO or 100Al 2 O 3 +lOOCaO) was placed 
in the furnace, 250 grams being used. When this was fluid, 700 
grams of a mixture of chrome ore and ferrosilicon was added. About 
140 grams of metal was obtained, which contained 38.05 per cent 
chromium, 3.09 per cent silicon, and 1.56 per cent carbon. In another 
experiment the metal contained 43.16 per cent chromium, 2.53 per 
cent silicon, and 0.S7 per cent carbon. There seems to have been a 
heavy loss through slagging of chromium. From these experiments 
it is evident that the resulting alloy from reduction with silicon will 
be high in silicon and also contain considerable carbon if there is any 
present in the silicon used. 

a Neumann, G., Herstellung von Ferro-liegierung ini elektrisehen Ofen: Stahl und Eisen, vol. 28, 
1908, p. 356. 



128 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


MOISSAN. 

Moissan a reduced chromite in the electric furnace with carbon as 
a reducing agent and obtained a ferrochrome that contained 60.9 
per cent chromium, 31.6 per cent iron, 6.1 per cent carbon, and 1.1 
per cent silicon. He also conducted experiments on decarburiza¬ 
tion of ferrochrome. A ferrochrome containing 61.81 per cent chro¬ 
mium, 30.02 per cent iron, 7.53 per cent carbon, and 0.33 per cent 
slag was broken into pieces and fused under a bath of liquid lime. A 
fine ground metal was obtained, which contained 64 per cent chro¬ 
mium, 35.12 per cent iron, 0.70 per cent carbon, and 10.22 per cent 
slag. 

EXPERIMENTAL SMELTING OF CHROMITE ^ IN THE ELECTRIC 

FURNACE. 

CONSTRUCTION OF FURNACE USED. 

Some experiments were made by the writer b in 1912 on the pro¬ 
duction of ferrochrome from chromite with carbon as a reducing 
agent. The experiments were performed in a furnace lined with 
magnesite, having one upper graphite electrode and a conducting 
hearth of iron rods embedded in magnesite. The interior dimensions 
of the crucible were: Width 4 inches, length 8 inches, and depth 8 
inches. The furnace took 8 to 12 kilowatts of single-phase current 
at 30 to 50 volts. The furnace held 12 to 15 pounds of the cold 
charge. 

MATERIALS USED IN CHARGE. 

The chromite used was a foreign grade used commonly for furnace 
linings. Analyses of the chromite, coke, lime, and fluorspar used 
are given below: 


Analyses of raw materials used in making ferrochrome. 


Chromite. 

Coke. 

Lime. 

Fluorspar. 

Constituent. 

Per cent. 

Constituent. 

Per cent. 

Constituent. 

Per cent. 

Constituent. 

Per cent. 

Cr 2 03 . 

1 46.35 

Fixed carbon.. 

.81. 43 

CaO... 

92 76 

CaF 2 

on nn 

FeO. 

2 21.45 

Volatile com- 


SiO.,. 

1.34 

CaCO-, 

80 

Si0 2 . 

5.48 

busti b le 


AI 2 O 3 —Fe 2 03 .. 

1.90 

A LO-j. 

8. 50 

AI 2 O 3 . 

12. 80 

matter. 

.25 

MgO 

Trace 



MgO. 

10. 08 

Ash. 

17.92 

P. 

.06 



CaO. 

Trace. 

Moisture . 

.35 




P. 

.013 

FeO. 

1.20 





S . 

.45 

Si0 2 . 

13.62 







CaO. 

.85 







P. 

.08 







s . 

.54 






1 31.7 per cent Cr. 2 ir. 6 per cent Fe. 

a Moissan, H., The electric furnace, p. 152. Translated by V. Lenher, 1904. 

b Keeney, R. M., The production of steels and ferro-alloys directly from ore in the electric furnace: Iron 
and Steel Inst. (Carnegie Scholarship Memoirs), vol. 4,1912, p. 108. 



















































FERROCHROME. 


129 


Iii these experiments, contrary to the usual European practice in 
ferrochrome manufacture, lime was used as a flux to show its desul¬ 
phurizing and dephosphorizing effect with an ore not so pure as the 
usual ore used in ferrochrome production. In usual practice only 
the most pure raw materials available are charged, so as to avoid the 
excess slag caused by adding lime. The only slag formed is from the 
coal or coke and chromite. 

RESULTS OBTAINED. 

Five experiments were made in which the furnace was charged 
and tapped at the completion of reduction. In these experiments 
the chromium percentage of the alloy seemed to run considerably 
lower than had been calculated, although this result is explained in a 
measure by the fact that the carbon in the metal was not considered 
in calculating the theoretical percentage. The carbon content was 
high in all of the alloys and does not seem to be influenced by the 
carbon in the charge as long as there is excess, which was the case. 
The phosphorus content also was high in all of the products. Seem¬ 
ingly all of the phosphorus charged was concentrated in the metal. 
This was caused by the excessive reducing conditions which did not 
permit the slagging of the phosphorus as calcium phosphate. The 
ore contained considerable sulphur—0.45 per cent—but almost all 
of it passed into the slag, probably as calcium sulphide. There was 
considerable loss of chromium and iron in the slag. In some cases 
the percentage of iron in the slag exceeded that of the chromium, 
but in no case did the percentage of chromic oxide in the slag exceed 
9 per cent, or the percentage of chromium, 4.69 per cent, showing 
that in the endeavor to keep the carbon in the alloy low the propor¬ 
tion of coke added was not sufficiently in excess for complete reduc¬ 
tion or that the furnace was not hot enough. The former was probably 
the case, as the furnace was operated as an arc furnace throughout 
the experiments. 

In two experiments (Nos. 6 and 7 of table following) the furnace 
was left full and several tappings were made during the run, the usual 
practice of ferrochrome manufacture thus being followed. Com¬ 
mercial ferrochrome is usually 5 to 10 per cent carbon, containing 
60 to 65 per cent chromium. 

Details of the seven experiments mentioned above are presented 
in the following table: 



Details of experiments in the production of ferrochrome directly from ore. 


130 


TJTE ELECTRIC FURNACE IN METALLURGICAL WORK 


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FEREOCIIEOME. 


131 


In these experiments the percentage of chromium in the alloy 
closely approached the theoretical. The percentage of carbon was 
also lower in these alloys because of the decarburizing effect of the 
unreduced oxide in the charge above the molten metal. The slag 
loss of iron and chromium was higher in these runs than in the inter¬ 
mittent experiments because of unreduced oxide getting into the 
slag on tapping. 

A total of 50 pounds of ferrochrome was tapped during the 
experiments, or an average extraction of 69.5 per cent. The average 
iron content of the slag for all experiments was 13.4 per cent FeO 
(10.4 per cent Fe); the average chromium content of the slag was 
10.3 per cent Cr 2 0 3 (6.6 per cent Cr). In the intermittent experi¬ 
ments the average percentages in the slag were 12.1 per cent FeO 
(9.4 per cent Fe) and 8.07 per cent Cr 2 0 3 (5.32 per cent Cr). Thus, 
of the loss of 30.5 per cent of material that was not tapped, 11.9 
per cent was chromium and 18.6 per cent was iron, on the assumption 
that of the total average loss 39 per cent was chromium and 61 per 
cent iron. A large part of the ferrochrome not tapped stuck in 
the furnace. Although the average electrode consumption was 158 
pounds per ton, the figure obtained in experiment No. 6, 48.1 pounds, 
would probably be attained in practical operation. The average 
power consumption was 3.7 kilowatt-hours per pound, or 0.85 kilowatt- 
year per ton. 

The conclusions drawn are, first, ferrochrome can be easily manu¬ 
factured directly from chromite in the electric furnace; second, the 
percentage of carbon in ferrochrome can not be kept low by regulat¬ 
ing the carbon charged without excessive loss of chromium in the 
slag; third, the percentage of carbon in the ferrochrome must be 
regulated by decarburization with an oxide slag of iron or chromite 
after the slag from reduction has been tapped off; fourth, the pro¬ 
portions of silicon and phosphorus can not be kept low in the alloy 
under the strong reducing conditions necessary; fifth, sulphur can 
be easily slagged; sixth, as the addition of lime does not seem to 
aid in reducing phosphorus, it is advisable to use no lime but raw 
materials as pure as possible; and, seventh, the power consumption 
should not exceed 3.7 kilowatt-hours per pound of ferrochrome tapped 
or 0.85 kilowatt-year per ton. 

THEORY OF CHROMITE SMELTING. 

REDUCTION WITH CARBON. 

In the reduction of chromium from chromite to form ferrochrome 
with the iron reduced, reduction of chromic acid begins at 1,185° C. a 
Reduction takes place according to the reaction: 

Fe0.Cr 2 0 3 +4C=Fe.2Cr+4C0 

a Greenwood, H. C., Slade, R. E., and Pring, J. N., Reduction of refractory oxides, production of ferro¬ 
alloys, and formation of carbides: Trans. Chem. Soc. (England), vol. 93, 1908, p. 1484; Electrocliem. and 
Met. Ind., vol. 7, 1909, p. 119. 




132 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


A pure chromite ore contains 68 per cent Cr 2 0 3 and 32 per cent 
FeO. For reduction of pure chromite 30 parts of carbon are theo¬ 
retically necessary for every 100 parts of iron and chromium reduced. 
In practice this amount is exceeded considerably. In lerrochrome 
manufacture practically all of the reduction is performed by the 
solid carbon and not by carbon-monoxide gas. On the basis that 
the double carbide Fe 3 C.3Cr 3 C 2 forms in reduction with carbon as 
has been found to be the case, the reduction reaction is as follows: 

9FeO.9Cr 2 O 3 +50C=[2(Fe 3 C.3Cr3C 2 )+3Fe]+36CO 

The ferrochrome resulting would contain theoretically 10.4 per 
cent carbon, 31.4 per cent iron, and 58.2 per cent chromium. For 
reduction of 100 parts of this alloy 37 parts of carbon are necessary, 
the above reaction explaining the difference between the theoretical 
and the practical proportion of carbon necessary, if calculation is 
made on the assumption that the double carbide is not formed. 

Carnot and Goutal isolated Fe 3 C.3Cr 3 C 2 from ferrochrome contain¬ 
ing 59 per cent chromium and 9 per cent carbon. 0 They found 
3Fe 3 C.Cr 3 C 2 in chrome steel containing 2 per cent chromium and 2 to 
0.5 per cent carbon. In the electric furnace Moissan obtained Cr 3 C 2 . 
By treating 50 per-cent ferrochrome with hydrochloric acid Behren and 
Van Linge obtained Cr 3 FeC 2 which corresponds closely to the double 
carbide isolated by Carnot and Goutal. Williams b , using the electric 
furnace, obtained 3Fe 3 C.2Cr 3 C 2 . All of these researchers show the 
existence of double carbides of varying percentages but all consisting 
of Fe s C and Cr 3 C 2 . 

The characteristics of ferrochrome of different percentages of carbon 
are widely variable. All of the alloys described contain 60 per cent 
or more of chromium. Ferrochrome containing 0.5 per cent carbon 
is bright lead gray in color, with the structure parallel to the bed of 
cooling. It breaks with difficulty, has a high compressive strength, 
and is one and one-half times as magnetic as soft steel of about 0.2 per 
cent carbon. 

Ferrochrome containing 1.8 per cent carbon is gray in color, and 
breaks into thin plates many of which show faces of one-third 
millimeter perpendicular to the bed of cooling. Naturally, it is a 
little magnetic, but on magnetizing it has more than twice the 
magnetism of soft steel. 

The 2.5 per cent carbon ferrochrome has the gray color of polished 
aluminum. It is weak and is about as magnetic as soft steel. With 
3.6 per cent carbon, the alloy has a bright-gray color. It has little 
brittleness and has magnetism equal to ferrochrome containing 1.8 
per cent carbon. Ferrochrome containing 4.5 per cent carbon is 


a Guillet, L., Etude Industricl des Alliages Metallique, p. 419. 
b Robin, F., Traite des Metallographie, 1912, p. 301. 




FERROCHROME. 


133 


dull gray, has little brittleness, and has magnetism equal to that of 
soft steel. Ferrochrome containing 5.5 per cent carbon has the gray 
color of bright iron. It breaks up a little, has a lower compressive 
strength, and a magnetism equal to that of 5.5 per cent carbon. 
With 7.5 and 9 per cent carbon the ferrochrome is gray, contains tin- 
gray oriented needles, breaks up, has no magnetism, and is very 
porous. 

REDUCTION WITH SILICON AND OTHER REDUCING AGENTS. 

Several United States patents have been issued for the reduction 
of metallic oxides by the use of silicon as a reducing agent. The 
reaction is as follows: 

2Fe0.20r 2 0 3 +4Si=2Fe.4Cr+4Si0 2 

Thus for the reduction of 100 parts of ferrochrome containing 65 per 
cent chromium, 35 parts of silicon are necessaiy. In United States 
patents granted to F. M. Becket ° based on this reaction it is claimed 
that a ferrochrome with a silicon content as low as 0.01 per cent or 
less can be made by this method, although this possibility is not shown 
in the researches of Neumann with the silicon percentage of the alloy 
high. Patents based on about the same reaction, with ferrosili- 
con as a reducing agent have been granted to E. F. Price. 6 These 
processes are expensive, the silicon content in the alloy tends to be 
high, and as a result they are not widely used in actual manufacture. 

Keigelgen and Seward c reduce chromium oxide with calcium 
phosphide according to the reaction 

8Cr 2 0 3 ^3P a Ca 3 =3P 2 0 6 +9Ca0+16Cr 

With phosphide of iron they utilize the reaction 

5Cr 2 O 3 4-6PF 2 =3P 2 O 5 +Cr 10 Fe 

The method is not commercially applied. 

Becket d proposes the use of calcium carbide as a reducing agent. 
He claims that the calcium reduces the metals and that the carbon 
is oxidized or remains with the resulting alloy, according to the 
reaction 

3Fe0.3Cr 2 0 3 +4CaC 2 =3Fe.6Cr+4Ca0+8C0 

The method has not been used much commercially because of the 
expense. For the reduction of 100 parts of ferrochrome containing 
65 per cent chromium, 53 parts of calcium carbide are necessary. 

a 854018, May 21, 1907; 866561, Sept. 17, 1907; 891898, June 30, 1908. 
b 865609, Sept. 10, 1907; 852347, Apr. 30, 1907; 862996, Aug. 13, 1907. 
c u. S. Patent 878966, Feb. 11,1908. 
d U. S. Patent 898173, Sept. 8, 1908. 






184 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Rossi,® using aluminum as a reducing agent in the electric furnace, 
has produced ferrochrome containing 68.24 per cent chromium, 1.85 
per cent silicon, 1 per cent carbon, and 0.5 per cent aluminum from 
chromite containing 50.29 per cent Cr 2 0 3 , 16.01 per cent FeO, 10.72 
per cent A1 2 0 3 , 4.62 per cent Si0 2 , 16.61 per cent MgO, 0.01 per cent 
sulphur, and 1.15 per cent CaO. 

REFINING OF FERROCHROME. 

Decarburization of high-carbon ferrochrome is accomplished by 
melting the alloy with a slag of lime, chromite ore, and a little fluor¬ 
spar, according to the following reaction: 

2[2(Fe 3 0.30r 3 C 2 )+3 Fe]+7Fe0.7Cr 2 0 3 =25Fe.Cr 2 +28C0 

For each 100 parts of completely decarburized alloy 39 parts of pure 
chromite ore are necessary, or for each 100 parts of ferrochrome con¬ 
taining 10.6 per cent carbon, 31.3 per cent iron, and 58.1 per cent 
chromium, 36 parts of pure chromite ore are necessary for complete 
decarburization. The resulting alloy would contain 66.6 per cent 
chromium and 33.4 per cent iron. In practice the lime is added 
simply to flux any silica in the ore, to assist in elimination of silicon 
in the ferrochrome, and to cause possible removal of carbon as calcium 
carbide, as the operation is performed in an arc furnace. The fluor¬ 
spar makes the slag more fluid. Gin 6 claims that high temperature 
is not necessary for decarburizing, but his contention is not sustained 
in practice. 

E. F. Price 0 proposes to decarburize ferrochrome by passing an 

oxidizing gas through the molten metal, but the process is not used 
in practice. , 

F. M. Becket d proposes to make a ferrochrome high in silicon, con¬ 
taining approximately 51.3 per cent chromium, 17.5 per cent iron, 
30 per cent silicon, and 1.2 per cent carbon in a first stage. Then he 
proposes to remove the silicon by adding chromite in the proportion 
of 6 parts of chromite to 1 part of silicon in the alloy, this proportion 
of chromite being slightly in excess of that theoretically necessary 
to oxidize all the silicon to silica. He gets an alloy containing 70 per 
cent chromium, 28.9 pel cent iron, 1 per cent carbon, and 0.10 per 
cent silicon. The necessity of such a refining process shows the weak¬ 
ness of methods using ferrosilicon or silicon as a reducing agent in 
that the percentage of silicon in the alloy can not be kept low in one 
operation without high losses of chromium in the slag. 

a Rossi, A. J., Ferro-alloys: Min. Ind., vol. 12, 1903, p. 693. 

b Gin, G., Decarburization of ferro-alloys: Trans. Electrochem. Soc., vol. 15, 1909, p. 225. 
c U. S. patent 886858, May 5,1908. 
d U. S. patent 891898, June 30, 1908. 





FERROCHROME. 


135 


MANUFACTURE OF FERROCHROME. 

Until the introduction of the electric furnace in 1899 ferrochrome 
was manufactured entirely in either the crucible or the blast furnace. 
The crucible was used only for the production of the higher grades, 
chromite being reduced with charcoal, and a flux of lime, borax, 
fluorspar, or water glass being used. In the blast furnace chromite 
is reduced with some difficulty, with the high fuel consumption of 
about 3 tons of coal or coke to 1 ton of ferrochrome produced. Theo¬ 
retically, it should be possible to get a ferrochrome containing 65 
per cent chromium from ore containing 60 per cent Cr 2 0 3 and 20 
per cent FeO, but generally a ferrochrome containing 30 to 40 per 
cent chromium and 6 to 12 per cent carbon is the product in the 
blast furnace. Little ferrochrome is now made by either the crucible 
or the blast furnace, because it can be made cheaper in the electric 
furnace in localities where electric power is cheap. A small amount 
of carbon-free ferrochrome is now made by the thermit process. 

ORES AND RAW MATERIALS USED. 

The greater part of the ores now used in the electric furnace manu¬ 
facture of ferrochrome come from Turkey, New Caledonia, Cuba, and 
New South Wales. There are considerable deposits of chromite ore 
in Canada and California, but they are so far from the market that the 
production does not amount to much. The analyses of some of the 
ores are given below: 

Analyses of chromite ores. 


Component. 

Turkey. 

Source 

New Cale¬ 
donia. 

of ore. 

Califor¬ 

nia. 

Cuba. 


Per cent. 

Per cent. 

Per cent. 

Per cent. 


51. 7 

55. 7 

52. 68 

50.0 

FeO 1 . 

14. 2 

13.2 

15.30 

18.57 


14. 1 

16.2 

11. 40 

12.44 

MgO". 

14.3 

9.3 

16.23 

13. 38 

Si0 2 . . 

3.5 


3.40 

3.82 

CaO" . 

1.7 

.25 


2 . 16 

h 2 o . 

.3 

1.05 

.94 


MnO . 


.2 

. 15 


P 2 O 5 . 


. 05 


. 45 

s .•. 




.69 







The foreign manufacturers use only chromite containing less than 
0.1 per cent phosphorus and sulphur and about 50 per cent Cr 2 0 3 . 
They use no lime in the charge, as it has been found preferable by 
them to use pure materials and keep the amount of slag as low as 
possible. In most plants high-grade anthracite coal is used as the 
reducing agent. The only American manufacturers of ferrochrome, 
44713°—Bull. 77—16-10 

































136 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

according to their patent specifications, use a lime slag. They some¬ 
times use Cuban ore, which contains considerable phosphorus and 
sulphur. Coke or charcoal may be used instead of anthracite coal, 
but the latter is better, as it may be obtained in a more finely pulver¬ 
ized state, a form in which it makes a more intimate contact with 
the chromite, and consequently produces a better reduction. As 
the electric furnaces have not a high shaft it is not necessary to use a 
reducing material of high compressive strength. 

TYPES OF FURNACES USED. 

There are several types of electric furnace used in the manufacture 
of ferrochrome. All are constructed on the principle of the Sieman’s 
crucible with a conducting hearth, or are similar to the Heroult steel 
furnace with vertical electrodes in series. In a conducting-hearth 
furnace the lining of the walls may be of chromite or, more commonly, 
magnesite or dolomite tar mixture, with a carbon block in the bottom; 
or, as in the Girod furnace, it may have a conducting hearth of iron 
rods buried in the refractory bottom; or, as in the Sieman’s furnace, 
it may have a nonconducting hearth in which the lining of the hearth 
and walls is entirely of a noncarbon refractory, such as dolomite, 
magnesite, or chromite. The walls are thin, not over 9 inches thick, 
but the electrodes are far enough from them to allow the molten charge 
to freeze on the walls and thus form a highly refractory lining. Some 
furnaces were water cooled at first to assist this result, but few are 
now so constructed. Ferrochrome freezes to a certain extent on the 
bottom, so that molten metal does not have so much chance to come 
in contact with the carbon bottom. 

PROCESS OF MANUFACTURE. 

4 

The process of manufacturing ferrochrome consists of mixing a 
charge of chromite and anthracite coal in proportions based upon the 
theoretical calculations given. The charge is shoveled into the open 
top of the furnace and around the electrodes. The furnace is charged 
at regular intervals so as to keep the top in an unfused condition. f ^he 
ore is finely powdered, but the coal is about as it comes from the min 
There is some loss of ore that is carried off with the gases that escap 
at the top of the furnace. At intervals of two to four hours the 
ferrochrome is tapped off from the bottom into iron pots set on cars, 
Irom which it and any slag are dumped when solid. The slag and 
metal come out of the same tap hole. When cool the metal is broken 
with hammers to separate it from the slag, and is packed into kegs 
or boxes. In tapping an iron rod is used to open up the tap hole, 
which is plugged with fire clay. 


FERROCHROME. 137 

Ferrochrome manufacture is carried on continuously, in some cases 
for two years, before the furnace is shut down for repairs. Ferro- 
chrome containing as low as 5 per cent carbon can be made economi¬ 
cally when produced directly from ore in one operation. It has been 
possible to produce an alloy containing as low as 2 per cent carbon in 
one operation, but great care in regulation of the charge and operation 
of the furnace is necessar} 7 ". The slags from the average ferrochrome 
furnace making a 5 per cent carbon alloy run from 0.5 to 1 per cent 
Cr 2 0 3 . 

The refining of the high-carbon grades of ferrochrome is done in 
an arc furnace where the alloy is subjected to a prolonged heating 
with a slag of chromite, lime, and fluorspar, proportioned to the 
amount of carbon and silicon to be removed and the silica that must 
be fluxed in the chromite used. The ferrochrome covered by this 
slag is heated at a high temperature for a length of time dependent 
on the carbon in the alloy. The resulting slag contains about 25 
per cent Cr 2 0 3 and is ground up and sent through the smelting 
furnace again, so that there is not much loss of chromium. By this 
method it is possible to reduce the carbon from 10 to 0.25 per cent, 
but the more usual low-carbon grade contains 0.5 per cent carbon. 
The percentage of carbon in the ferrochrome varies from 9.5 to 0.6 
per cent carbon, but the iron increases with the decrease of carbon. 
This would seem to show that in refining, the iron oxide of the chro¬ 
mite is first reduced, the chromic oxide merely serving to keep a slag 
with excess chromium, thus preventing any final lowering of the 
percentage of chromium in the alloy. As the carbon is oxidized so 
is the silicon until the content is as low as 0.2 per cent, as compared 
with 2 to 5 per cent in the crude alloy. Aluminum is also consider¬ 
ably eliminated, and phosphorus and sulphur are reduced to a slight 
degree. Although the market is small for ferrochrome very low in 
carbon, the difference in price between the 9 per cent alloy and the 
0.5 per cent product does not seem warranted. The refining expense 
is almost entirely the cost of power, and with the cheap power gener¬ 
ally available at a ferro-alloy plant the expense is not as high as 
$300 per ton, the difference in price of the products mentioned. 

Processes based on the use of silicon or some reducing agent other 
than carbon have not been commercially successful because the cost 
of such reducing materials as silicon, ferrosilicon, and aluminum is 
much higher than that of carbon. Also the products may be con¬ 
taminated with the reducing material just as when carbon is used, 
so that a subsequent refining is necessary. Carbon-free ferrochrome 
for high-grade steels has, however, been successfully made by the 
thermit process, but the amount made in this way is comparatively 
small. Analyses of various grades of ferrochrome follow. 


138 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Analyses of typical ferrochromes. 





Electric furnace. b 

Component. 

Crucible.a 

Blast 
furnace.a 

With 8 
to 10 per 
cent 
carbon. 

With 7 
to 8 per 
cent 
carbon. 

With 5 
to 0 per 
cent 
carbon. 

With 3 
to 4 per 
cent 
carbon. 

With 1 
per cent 
carbon. 

Chromium. 

Per cent. 
19.8 

Per cent. 
41.39 

Per cent. 
04.5 

Per cent. 
63.5 

Per cent. 
04.0 

Per cent. 
04.0 

Per cent. 
03.5 

Iron. 


22.0 

21.5 

28.5 

31.0 

3.5 

35.0 

Carbon. 

3.8 

7.12 

9.5 

7. 5 

5.5 

.6 

Silicon . 

.21 

2. 25 

5.8 

.4 

.3 

.2 

\luminum. 


.SO 

.8 
. 15 

.5 

.4 

. 10 

Manganese. 

.33 

1.84 

.15 

. 15 

. 15 

. 10 

Calcium. 

.25 

.25 

.25 

.30 

.35 

Sulphur. 



.04 

.04 

.04 

.04 

.03 

rhosphorus. 


.052 

.03 

.03 

.03 

.02 

.02 



c. 


a Venator, W., Uber Eisen Liegierungen und Metall fiir die Stahl Industrie: Stahl und Eisen. vol. 28, 
1908, p. 41. 

b Girod, P., Studies on the electrometallurgy of ferro-alloys and steel: Trans. Faraday Soc., vol. 11, 1911, 
172. 

POWER AND ELECTRODE CONSUMPTION. 

The power consumption in a ferrochrome furnace of the Meraker 
Electric Smelting Co., at Kopperaaen, Norway, was recently given as 
3 kilowatt-hours per pound, or 0.68 kilowatt-year per short ton in 
making a ferrochrome containing 5 per cent carbon. At Kanawha 
Falls, W. Va., ferrochrome was made in a crucible electric-arc furnace 
with a power expenditure of 3.6 kilowatt-hours per pound, or 0.72 
kilowatt-year per ton. a This product contained 70.96 per cent 
chromium, 23.23 per cent iron, 5.21 per cent carbon, 0.5 per cent 
silicon, 0.008 per cent phosphorus, and 0.078 per cent sulphur. 
At both Kopperaaen and Kanawha Falls an ore containing about 50 
per cent Cr 2 0 3 was used. The Kopperaaen ferrochrome contains 65 
to 70 per cent chromium. In the experiments of the writer, which 
have been described, a product containing 50 to 68 per cent chro¬ 
mium and 4.32 to 9.31 per cent carbon was obtained with an ore 
containing 46.35 per cent Cr 3 0 3 , 3.02 kilowatt-hours per pound or 
0.69 kilowatt-years per ton. A 750-kilowatt furnace of the Alby- 
carbide type at Kopperaaen, operating continuously, uses on the 
average about 3 kilowatt-hours per pound of ferrochrome produced, 
or 0.68 kilowatt-year per short ton, when chromite ore containing 
50 per cent Cr 2 0 3 is charged; and the product contains 5 per cent or 
more of carbon and 65 per cent of chromium. 

The electrode consumption in ferrochrome manufacture depends 
somewhat on the proportion of carbon in the ferro-alloy being pro¬ 
duced, as, if the carbon of the charge be materially reduced, the 
electrode will be oxidized by the charge. With an open-top furnace 
the consumption varies from 50 to 100 pounds per short ton of ferro- 

a S(;hoel, G. P., Manufacture of ferro-alloys in the electric furnace: Electrochein. Ind., vol. 2,1904, p. 450. 









































FERROCHROME. 


139 


chrome produced. As most of the ferrochrome furnaces do not use 
continuously feeding electrodes this item will probably be kept at a 
much lower figure in the future. At present in many plants one-half to 
one-third of the electrode is not used, and, unless the works has its 
own electrode plant in which stumps can be made into new electrodes, 
this is lost so far as its electrode value is concerned. Aside from the 
electrode item, the repair and up-keep cost on a ferrochrome furnace 
is not high. The linings last one to three years without repair. 


COST OF MANUFACTURE OF FERROCHROME. 

In the table following, estimates are made of the cost of manufac¬ 
ture of a ferrochrome containing 60 per cent chromium and 8 to 10 
per cent carbon from chromite ore containing 50 per cent Cr 2 0 3 . The 
power figures and other data were gathered by the writer in Europe 
and the United States during the past year. The calculations are 
on the- basis of two 750-kilowatt furnaces turning out a total of 6 
tons of ferrochrome per 24 hours. The Norwegian plant is within 
60 miles; the French plant within 200 miles, and the American plant 
assumed to be within 100 miles of seaboard. Labor conditions are 
considered to be as found in the various countries. 


Cost of production of ferrochrome per ton (2,000 pounds). 


Item. 


3,000 pounds of chromite.. 

500 pounds of coal.. 

50 pounds of carbon electrodes. 

0.08 kilowatt-year. 

Labor. 

Repairs. 

Amortization and depreciation at 5 per 

cent each. 

Interest on $50,000 at 6 per cent. 

General and packing. 


Total. 


Norway. 


Cost 
of unit. 


$15.00 
5.00 
.04 
8.30 
a 1.00 


Total 

cost. 


$20.50 
1.25 
2.00 
5.65 
8.33 
4.00 

2.50 

1.50 
4.00 


51.73 


France. 


Cost 
of unit. 


$15.00 
6.00 
.03 
18.66 
a. 80 


Total 

cost. 


$22.50 
1.50 
1.50 
12. 70 
6.66 
4.00 

2. 50 
1.50 
4.00 


56.86 


United States. 


Cost 
of unit. 


$15.00 
5.00 
.04 
26.66 
a 1.50 


Total 

cost. 


$22.50 
1.25 
2.00 
17. 65 
16. 60 
4.00 

2.50 

1.50 
4.00 


72.00 


a Minimum for eight hours. 


The figures indicate that it costs $20.27, or 39.2 per cent, more to 
manufacture ferrochrome in the United States than in Norwav. 
This increase is due to the higher price of power and increased labor 
cost here. The cheapest figure at which power can be obtained now 
in the eastern United States is $26.66 per kilowatt-year for electro¬ 
metallurgical purposes. The duty on ferrochrome is to be 15 per cent 
ad valorem. The 8 to 10 per cent grade sells for $110 to $130 per 
short ton (see table following). 












































140 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

SELLING PRICES OF FERROCHROME. 

Ferrochrome is sold on the basis of a chromium content of 60 per 
cent, the price varying with the percentage of carbon. As the per¬ 
centage of chromium varies from a given grade of alloy, the price, 
based on the carbon percentage, is decreased or increased a certain 
amount for each per cent variation from 60 per cent chromium. 
This feature is shown in the following tabulation of prices current in 
Germany and the United States on January 1, 1913: 

Prices offerro-alloys and metals. a 

GERMANY, F. O. B. DUISBURG. 


Alloy. 

V 

1912 


1913 

Oct. 1. 

Nov. 1. 

Dec. 1. 

Jan. 1. 

Ferrosilicon: 

Made in the blast fnrnace, basis 10 per cent silicon, 2,240 

pounds, scale ±$0.96.-». 

Made in the electric furnace, basis 45 per cent silicon, 2,240 
pounds, scale ±$1.51... 

$32.90 

73.00 

$34.90 

70.00 

$35. 40 

68.00 

$36.80 

70.00 

Made in the electric furnace, basis 75 per cent silicon, 2,240 
pounds, scale ±$1.65. 

129.00 

126.00 

126.00 

126 .00 

Ferromanganese silicon, electric furnace, 2,240 pounds: 

50 to 55 per cent manganese, 23 to 28 per cent silicon. 

112.00 

112.00 

112.00 

112.00 

68 to 75 per cent manganese’ 20 to 25 per cent silicon. 

50 to 55 per cent manganese, 30 to 35 per cent silicon. 

112.00 
117.50 

106.50 

117.50 

106.50 

117.50 

106.50 

117.50 

Ferromanganese, basis 80 per cent manganese, 2,240 pounds, 
scale ±$0.55. 

61.90 

61.90 

64.25 

68.00 

Ferrochrome: 

Carbon free, thermit process, basis 60 per cent chromium, 
2,000 pounds, scale $8.95. 

500.00 

500. (X) 

550.00 

550.00 

Electric furnace— 

Refined No. I, 0.3 to 0.75 per cent carbon, basis 60 per 
cent chromium, scale $8.85, 2,000 pounds. 

436.00 

436.00 

436.00 

436.00 

Refined No. II, 1 to 2 per cent carbon, basis 60 per cent 
chromium, scale $7, 2,000 pounds. 

262.00 

262.00 

262. (X) 

262.00 

4 to 6 per cent carbon, basis 60 per cent chromium, scale 
$4.20, 2.000 pounds. 

105.00 

112. 25 

118.50 

133.00 

Ferroutanium (10 to 15 per cent titanium), per pound. 

.188 

. 75 

. 188 

. 188 

. 188 

Ferrotungsten, 85 per cent tungsten, 0.5 to 1 per cent carbon, 
per pound of tungsten contained. 

.71 

. 75 

. 765 

Ferromolybdenum, 70 to 80 per cent molybdenum, per pound 
of molybdenum contained. 

2.06 

2.06 

2.06 

2 06 

Nickel, 98 to 99 per cent nickel, per pound. 

.43 

.43 

.43 

43 

Aluminum, 98 to 99 per cent aluminum, per pound. 

.20 

.206 

.213 

218 

Tungsten metal, 96 to 98 per cent tungsten, per pound. 

.70 

.72 

.725 

.72 


UNITED STATES, F. O. B. PITTSBURGH, PA. 

Ferromanganese, basis 80 per cent manganese. 2,240 pounds.. 


863.30 

Ferrosilicon, blast furnace, f. o. b. Ashland, Ky.: 

10 per cent silicon. 




24 00 • 

11 per cent silicon. 




25. 00 
26.00 
75.00 

12 per cent silicon. 




Ferrosilicon, electric furnace, 50 per cent silicon, 2,240 pounds.. 




Ferrotitanium, 10 to 15per cent titanium, f. o. b. Niagara Falls, 
N. Y., per pound in carloads. 




.08 

2.50 

Ferro vanadium, per pound of vanadium content. 









a Stahl und Risen, vol. 33,1913, p. 85 (revised). 


USES OF FERROCHROME. 

Ferrochrome is used extensively in the manufacture of steel for 
armor plates, armor-piercing projectiles, wire, bullet-proof steel, tool 
steel, high-speed steel, high-grade castings, stamp-mill shoes and 


































































FERROMANGANESE. 


141 


dies, safe steel, tires, axles, springs, razors, file and cutlery steel, and 
for many other purposes. As shown int he table on page 138, electric 
furnace ferrochrome is made in five grades, of which those contain¬ 
ing 4 per cent carbon are classed as refined, the carbon in the others 
being regulated in the charge to a certain extent. 

Ferrochromes containing less than 2 per cent carbon are used in the 
manufactures of tool steels and high-speed steels. The alloy contain¬ 
ing 3 to 4 per cent chromium is used principally in the manufacture 
of steel castings. For general open-hearth casting ferrochrome con¬ 
taining 4 to 6 per cent of carbon is used. 

For the manufacture of armor plate and projectiles, the high-car¬ 
bon ferrochromes containing S to 9 per cent carbon are generally 
used. This alloy is much cheaper and also its use is advisable for 
armor plate, because the carbon must be added at some time to 
harden the steel. A ferrochrome containing a high proportion of 
carbon used in the open-hearth furnace will give a yield much supe¬ 
rior to that containing a low proportion of carbon, because if the metal 
is still slightly oxidized, the oxide will act on the carbon rather than 
on the chromium. For the purpose of protecting the chromium from 
oxidation, armor-plate manufacturers use a ferrochrome that con¬ 
tains a high percentage (4 to 5 per cent) of silicon. In this way the 
oxides act on the silicon before they act on the chromium. 

The distinguishing feature of chrome steels is their great hardness. 0 
Chrome steels usually contain 1 to 2 per cent chromium and 0.8 to 2 
per cent carbon. Armor plate contains about 3.25 per cent nickel, 
1.5 per cent chromium, and 0.25 per cent carbon. In armor plates 
the nickel and chromium are sometimes added in the form of a ferro- 
chrome-nickel containing 52 per cent chromium, 18 per cent nickel, 
28.96 per cent iron, 0.5 per cent carbon, 0.5 per cent silicon, 0.03 per 
cent sulphur, and 0.01 per cent phosphorus. 

FERROMANGANESE. 

HISTORY. 

In steel manufacture more ferromanganese than any other ferro¬ 
alloy is used. The industrial importance of ferromanganese began 
in 1866 with the introduction of the Bessemer process, which required 
a strong deoxidizing agent to produce a sound steel. In 1866, Prieger 
of Bonn, Germany, made in the crucible some ferromanganese con¬ 
taining 70 to 80 per cent manganese. At Terre-Noire, France, a 
little later it was made in the open-hearth furnace and crucible in a 
combination process. The first ferromanganese to be made in the 
blast furnace was produced in Sweden in 1873, and contained 33 
per cent manganese. In 1875, at Terre-Noire, Pourcel made in the 
blast furnace some ferromanganese that contained 75 to 80 per cent 


a Stoughton, Bradley, The metallurgy of iron and steel, 1908, p. 399. 






142 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


manganese. Since that time up to a few years ago all ferromangan¬ 
ese was made in the blast furnace. At present a comparatively 
small quantity is made in the electric furnace, the greater part of 
that so made being used for the production of ferromanganese-silicon or 
silicomanganese. When the iron-manganese alloy contains less than 
25 per cent manganese it is called spiegeleisen; when it contains 
more than 25 per cent it is called ferromanganese. 

EXPERIMENTS IN THE PRODUCTION OF FERROMANGANESE. 

Stassano ° in 1908 made some experiments in the production of 
ferromanganese in a 75-ldlowatt electric furnace of the type of the 
Stassano steel furnace. The charge consisted of 1,000 parts of man¬ 
ganese ore, 300 parts of charcoal, 60 parts of lime, and 80 parts of 
25 per cent sodium silicate used as a binder for briquets of the above 
composition, the form in which the charge was smelted. The ore 
used contained 45.65 per cent Mn 3 0 4 , 16.1 per cent Fe 2 0 3 , 3.05 per 
cent A1 2 0 3 , 30.16 per cent Si0 2 , 0.15 per cent BaO, 1.2 per cent CaO, 
0.43 per cent MgO, 0.817 per cent S, and 0.34 per cent P. The 
desired product was to be silicomanganese containing about 60 per 
cent manganese and 20 per cent silicon. The charge was submitted 
to the heat radiated from the arc as in all Stassano furnaces. 

The product contained 17.76 per cent iron, 17.6 per cent silicon, 
62 per cent manganese, 1.8 per cent carbon, 0.028 per cent phosphorus, 
and a trace of sulphur. No data showing the losses of manganese 
were given. The energy consumption was 3.86 kilowatt-hours per 
pound, or 7,560 kilowatt-hours, 0.86 kilowatt-year, per long ton. 

THEORY OF PRODUCTION. 


Ferromanganese is manufactured from manganese oxide ore with 
carbon as a reducing agent. Because of the high reduction point of 
manganese dioxide, 1,105° C., considerably more coke is necessary 
in the blast-furnace charge than in the iron blast furnace. Reduc¬ 
tion takes place in the electric furnace according to the reaction— 


Mn0 2 +2C=Mn+2C0. 


For the reduction of 100 parts of manganese, 43.5 parts of carbon 


are necessary. 

Carnot h and Goutal have shown the existence of the following: 
double carbides of iron and manganese in ferromanganese of different 
percentages of carbon: 

Percentage of 

Double carbide. manganese. 


Fe 3 C. 4 Mn 3 C. 74 to 85 

Fe 3 C. 2 Mn 3 C. 60 to 74 

2Fe 3 C. Mn 3 C. 30 to 60 

4Fe 3 C. Mn 3 C. below 18 


a Stassano, E., Treatment of iron and steel in the electric furnace: Electrochem. and Met. Ind., vol. 6, 
1908, p. 315. 

b Guillet, L., Etude iudustriel des alliages metalliques, p. 405. 








143 


FERROMANGANESE. 

The single carbide of manganese is Mn 3 C, similar to Fe 3 C, the 
carbide of iron. 

Ferromanganese usually contains about 6 per cent carbon, when it 
is silvery white. When the silicon content in the alloy is low, the 
carbon is all in the combined state. With more than 5 per cent silicon 
the carbon falls to about 2 per cent, and as the silicon increases the 
carbon in the alloy decreases. 

PROCESS OF MANUFACTURE. 

Ferromanganese is still manufactured almost entirely in the blast 
furnace. When the manufacture of ferro-alloys in the electric furnace 
began, attempts were made to make ferromanganese. These failed, 
chiefly because of operation of the electric furnace at so high a tem¬ 
perature as to produce great volatilization of the manganese. As the 
electric furnace became better understood, heating by resistance only 
was found possible, thus insuring a low enough temperature. 

Most of the blast-furnace ferromanganese used in this country, 
with the exception of that made by one large corporation, is made in 
England. Recently some German ferromanganese has been put on 
the market. Russian or Turkish manganese oxide ore is used. Ores 
high in silicon can not be used because of the high loss of manganese 
as silicate in the slag. The results of a typical blast-furnace run, 
including figures as to the ore used, and the slag and the alloy pro¬ 
duced, are given in the table below. In this run the average amount 
of coke consumed was 2.37 long tons per long ton of ferromanganese 
produced. Of the total manganese charged 76.9 per cent was saved 
and 23.1 per cent lost. Of the total slag lost 6.7 per cent was in the 
slag and 18.4 per cent was volatilized or lost as dust. 


Results of blast-furnace run to 'produce ferromanganese. 11 


Ore. 

! 

Slag^ 

F erro manganese. 

Constituent. 

Percentage. 

Constituent. 

Percentage. 

Constituent. 

Percentage. 

"Mn 

51.6 

Si0 2 . 

30.32 

Mn. 

80.20 

Fe 

1.45 

FeO'. 

1.41 

Fe. 

11.80 

p 

.173 

MnO. 

8 . 52 

Si. 

1.16 

Si0 2 

7.80 

AI 9 O 3 . 

10 . 88 

P. 

.38 


1.12 

CaO.’.. 

41.34 

C. 

6.46 

CaO . -- 

1.80 

MgO. 

2.96 



MeO 

2.18 

P 2 0 6 . 

.01 



RaO . 

2.20 

CaS. 

3.94 





BaO. 

.48 




a Jakoki, J., Ferromangen in Hochofen; Stahl und Eisen, vol. 29,1909, p. 1191. 


The loss of manganese by volatilization, or as dust, varies between 
15 and 30 per cent of the total quantity of manganese charged. The 
average total loss is about 30 per cent, of which 10 per cent goes to the 
slag and 20 per cent is volatilized or lost as dust. Any phosphorus 













































144 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

in the ore goes to the metal, but there is no difficulty in slagging the 
sulphur. No more than 0.02 per cent of phosphorus should be present 
for each 10 per cent of manganese in the ore. The manganese as a 
rule is unevenly distributed through the alloy. Usually some lime¬ 
stone is necessary in the charge. The alloy produced in the run dis¬ 
cussed above is high in phosphorus. An average English ferroman¬ 
ganese contains 83.4 per cent manganese, 9.04 per cent iron, 6.5 per 
cent carbon, 0.8 per cent silicon, 0.25 per cent phosphorus, and 0.01 
per cent sulphur. 

When ferromanganese is being made in the electric furnace, the 
electrodes and voltage are regulated so as to prevent arching. With 
a mixture of 813 parts of ore containing 30 per cent manganese, 178 
parts of anthracite coal (4 to 5 per cent ash), and 90 parts of fluorspar, 
about 450 pounds of product was obtained per ton of mixture treated. 
The product contained 85 per cent ferromanganese.® Of the total 
manganese charged 26.8 per cent was lost by volatilization, as dust, 
and in the slag. Ferromanganese made in the electric furnace has 
considerably lower carbon content than the blast-furnace ferroman¬ 
ganese, and is used in the molten state by the ferro-alloy manufac¬ 
turer for making silicomanganese. 

USES OF FERROMANGANESE. 

The greater part of the ferromanganese manufactured is used in 
the deoxidation and recarburization of ordinary Bessemer and open- 
hearth steel. It is a strong deoxidizing agent and also assists in the 
elimination of sulphur from steel. In foundry work ferromanganese 
is used for softening, strengthening, and purifying hard or chilling 
iron. It is also employed for strengthening soft iron. 

The next greatest use for ferromanganese is as a fixed addition in 
the production of manganese steel. When the manganese content of 
steel is more than 1 per cent, the metal becomes hard and somewhat 
brittle, and these qualities increase in intensity with every increase 
of manganese up to 4 to 5.5 per cent when the steel can be powdered 
under the hammer . b With 7 per cent manganese new properties 
appear, which are well marked in steel having a manganese content 
of 10 per cent, and reach a maximum with a manganese content of 12 
to 15 per cent. Manganese steel usually contains 12 to 13 per cent of 
manganese and 1.5 to 2 per cent of carbon. With that proportion of 
manganese the strength and durability of the metal is at its maxi¬ 
mum. When cooled slowly after casting manganese steel is almost 
as brittle as glass. It must be reheated and quenched at a high tem¬ 
perature in water. After such treatment it is as ductile as soft car¬ 
bon steel or wrought iron, and its tensile strength is about three times 


a Guillet, L., Etude industriel des alliages mdtalliques, p. 405. 
b Stoughton, B., The metallurgy of iron and steel, 1911, p. 397. 




FERROMANGANESE-SILICON. 


145 


as great. The hardness of the product after the latter treatment is 
almost the same as before, being so hard that machining is not prac¬ 
tical. The forging and working of manganese steel is very difficult 
and is understood by only a few. 

Manganese steel is used for the jaws and wearing parts of rock¬ 
crushing machinery, for railroad frogs and crossings, for railroad rails 
on curves, for mine-car wheels, and for burglar-proof safes. Because 
of its great hardness without brittleness its life for the uses mentioned 
is many times that of all other steels. 


FERR O MAN GANES E-SILICON. 

Ferromanganese-silicon or silicomanganese is an alloy developed 
since use has been made of the electric furnace for ferro-alloy manu¬ 
facture. Ferromanganese is made from manganese ore in an electric 
furnace operated as a resistance furnace, and ferrosilicon is made in 
a separate arc* furnace. The two products are mixed while hot in a 
ladle, to form the alloy of the desired percentage of manganese and 
silicon. Ferromanganese containing about 85 per cent of manganese 
is made. The percentage of ferrosilicon depends on the amount of 
iron desired in the finished silicomanganese. The other method of 
manufacture is to mix coal, quartz, manganese, oxide ore, and iron 
turnings in the proper proportion to form the desired silicomanganese 
and smelt it all in one furnace which must be kept at a high tempera¬ 
ture because of the high reduction point of silica. The great disad¬ 
vantage of this method is the high loss of manganese by volatilization. 
This method, however, seems to be the favorite one, as it is quicker, 
only one furnace is involved in the process, and less labor is necessary. 
It should be noted from the table on page 140 that the price of silico¬ 
manganese does not increase with the manganese content hut with an 
increase in the percentage of silicon. This is because much more 
energy is necessary for reduction of silica than of manganese oxide. 
A third method of manufacture is to reduce rhodonite (MnSi0 3 ) with 
carbon in the electric furnace. In this method coal or coke is mixed 
with rhodonite containing 38 per cent manganese, in the proportion 
of 600 parts of ore to 100 parts of coke. The electrode consumption 
is very high, being about 200 pounds per ton of product, and the 
power consumption is 5,400 kilowatt-hours or 0.62 kilowatt-year per 
ton. Keller adds ferrosilicon to a fused mixture of ferrosilicon, quartz, 
carbon, and manganese ore, claiming that the reduction temperature 
remains low and prevents volatilization of manganese. 

Three grades of ferromanganese-silicon are made as follows: 50 to 
55 per cent manganese, 23 to 28 per cent silicon; 68 to 75 per cent 
manganese, 20 to 25 per cent silicon; 50 to 55 per cent manganese, 
30 to 35 per cent silicon. The carbon content in these alloys is low, 


146 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

owing to the action of silicon in breaking up the combined carbon in 
the ferromanganese, causing the carbon to separate as graphite, 
which rises to the surface of the bath. With less than 16 to 18 per 
cent silicon in the alloy, carbon remains in the combined state; with 
more than that percentage, any carbon present is in the form of 
graphite. Analyses of typical silicomanganese are given below: 


Analyses of typical fcrromanganese-silicon. 


Constituent. 

Analysis 1. 

Analysis 2. 

Analysis 3. 

Silicon. 

Per cent. 
24.1 

Per cent. 
24.6 

Per cent. 

24 1 

Manganese. 

74.2 

70.3 

55. 0 

Iron. 

.77 

3.8 

19.0 

Aluminum. 

.4 

. 4 

Calcium. 


.3 

.3 

Magnesium. 


.2 

2 

Carbon.-. 

.30 

.35 

. 35 

Sulphur. . 

.01 

.02 

02 

Phosphorus . 

.02 

.04 

.04 



Alloys similar to those represented in analyses 1 and 2 are used for 
incorporating manganese and silicon in steel. The alloy is also used 
for deoxidizing, when a composition similar to that given in analysis 
3 is generally employed. The product has the advantage over ferro¬ 
manganese of being low in carbon, yet possessing as strong a deoxi¬ 
dizing power. Its use is especially advantageous in making high- 
grade manganesesilicon steel. Silicomanganese is usually added to 
the furnace just before the furnace is tapped, or in the casting ladle 
during tapping. 

ELECTRIC SMELTING OF MOLYBDENITE AND THE 
PRODUCTION OF FERROMOLYBDENUM. 

HISTORY. 

Ferromolybdenum is generally manufactured in the electric furnace 
from the raw sulphide ore of molybdenum, molybdenite. It is also 
made by the reduction of the roasted sulphide with carbon in a crucible 
or an electric furnace. The alloy is not widely used because of its 
high cost, which is caused by the irregularity of the ore supply. With 
a better and steadier source of ore, ferromolybdenum would probably 
be used in place of ferrotungs 4 ten. Ferromolybdenum was made from 
roasted ore in the crucible before the introduction of the electric fur¬ 
nace, but has been produced commercially directly from the sulphide 
only since 1900, following the use of the electric furnace. 

INVESTIGATORS. 

Investigators of the electric smelting of molybdenite or of the pro¬ 
duction of ferromolybdenum are mentioned below, their methods 
being briefly outlined. 























ELECTRIC SMELTING OF MOLYBDENITE. 


147 


GUICHA11D. 

Guichard,® working with Moissan between 1890 and 1895, obtained 
a crude molybdenum from natural molybdenite by reduction with 
carbon in the electric furnace. This product was really a carbide, 
as it contained 91.8 per cent molybdenum, 2J per cent iron, and 6.64 
per cent carbon. The operation was performed according to the fol= 
lowing reaction: 

2MoS 2 +3C=Mo 2 C+2CS 2 

The difficulty in the process is to obtain pure metal from impure ores, 
because there is a tendency for any impurities to concentrate in the 
metal. 

LEHNER. 

Lehner b conducted a series of experiments on the production of a 
ferromolybdenum free from sulphur, using molybdenite in the elec¬ 
tric furnace. After several unsuccessful experiments, in which the 
oxides of other metals were used to decompose molybdenite or in 
which the reducing agent was aluminum, he tried to accomplish the 
reduction in the electric furnace with a very basic slag, according to 
the following reaction: 

MoS 2 +2CaO+2C=Mo+2CaS+2CO 

The results of some of his experiments are tabulated below: 


Results of experiments of Lehner. 


Experiment No. 

1 

2 

3 

4 

5 

Charge: 







MoS-2. 

.pounds.. 

3.3 

3.3 

1.23 

5.5 

5.5 


.do_ 



2. 11 

4. 73 

4. 73 

CaO.. 

.do_ 

2.31 

3. OS 

.86 

a 9.16 

a 9.16 

Coke. 

. .do_ 

.55 

.85 

.79 

2.18 

2.18 

Product: 







Molybdenum. 

.percent.. 

90.7 

88.3 

43.30 

50.33 

48. 72 

Iron. 

.do_ 

2.9 

2.89 

49.8 

45.95 

46. 56 

Carbon. 

.do_ 

4.1 

5.60 

6. 27 

1.70 

1.06 

Silicon.. 

.do.... 


2. 95 

.31 

1.51 

2.61 

Sulphur. 

.do_ 

.86 

.04 

. 05 

.10 

.13 


a CaC 03 . 


These results show the possibilities of sulphur elimination by means 
of lime in the electric furnace, but do not show where the molyb¬ 
denum losses occur—whether in the slag or by volatilization. An 
extraction of 85 per cent was made in experiment 2. 

NEUMANN. 

Neumann c attempted reduction of molybdenite according to the 
reaction: 

MoS 2 +Si=Mo+SiS 2 . 


a Guichard, M., Sur la molybdenite et la preparation au molybdene: Compt. Rend., vol. 122, 1896, p. 
1270. 

b Lehner, W., Ilerstellung von Molybdenum: Metallurgie, vol. 3, 1906, p. 549. 

c Neumann, G., Herstellung von Ferroliegierung iin electrischen Ofen: Stahl und Risen, vol. 28, 1908, 
p. 356. 

































148 the electric furnace in metallurgical work. 


He obtained unsatisfactory results. The metal produced contained 
2.87 per cent iron, 2.06 per cent silicon, and 13.89 per cent sulphur, 
the remainder being molybdenum. Upon this method, several 
patents issued to Becket are based. 

EXPERIMENTS ON REDUCTION OF MOLYBDENITE. 

An experiment was made by the writer,® who used the electric 
furnace described in the discussion of the ferrochrome experiments to 
test the possibility of sulphur elimination with a charge of molyb¬ 
denum and excess lime, carbon being used as a reducing agent. The 
experiment was made directly after some experiments on the produc¬ 
tion of molybdenum steel directly from hematite and molybdenite, 
and can not be considered as quantitative, as the furnace lining was 
in poor condition. Some iron left in the furnace diluted the product. 
The electric furnace was regulated so that all heating was through 
resistance only. On tapping, 1.5 pounds of ferromolybdenum was 
obtained. The odor of sulphur was noticeable during the experiment. 
The product was brittle, but was not extremely high in sulphur in 
view of the amount of sulphur in the charge. There was 30 per cent 
sulphur in the ore, but only 0.19 per cent sulphur in the product. 
A commercial ferromolybdenum having 50 per cent of molybdenum 
contains about 0.03 per cent sulphur and 0.5 to 4 per cent carbon. 
The results of the experiment are shown in the table below. The 
coke, fluorspar, and lime had the composition given in the table on 
page 128. 

Production offerromolybdenum from molybdenite. 


Ore. 

Charge. 

Metal. 

Slag. 

Constituent. 

Percentage. 

Constituent. 

Pounds. 

Constituent. 

Percentage. 

Constituent. 

Percentage. 

Mo. 

47. 5 

Molybdenite 

4.0 

Mo. 

50.55 

Mo On 

Q 1 C 

Fe. 

1.23 

Coke. 

1.04 

C. 

. 73 

CaO " 

.±1 en 

Si0 2 . 

13.90 

Lime. 

3.01 

Si.... 

.94 

MaO 

1 9 

P. 

.608 

Fluorspar... 

.25 

P. 

.078 

FeO 

7.56 

S. 

30. 64 


S. 

.19 



From this experiment no conclusion can be drawn as to the loss of 
molybdenum, but in three runs made on the production of molyb¬ 
denum steel from hematite and molybdenite with carbon as a reduc¬ 
ing agent, the average total molybdenum loss was 46.1 per cent, of 
which 25.4 per cent was in volatilization and 20.7 per cent by slagging. 
Thus 56.2 per cent of the total molybdenum loss was by volatilization. 

The conclusions made from the ferromolybdenum experiment were: 
t irst, that ferromolybdenum low in carbon can be made directly from 
molybdenite in the electric furnace, with excess lime as a desulpliur- 

a Keeney, K. M,, I lie production of steel find ferro-alloys directly from ore in tlie electric furnacei Iron 
and Steel Inst., Carnegie Scholarship Memoirs, vol. 4, 1912, p. 108. 


















































ELECTRIC SMELT!XG OF MOLYBDENITE. 


149 


izing agent and carbon as a reducing agent; second, that a product 
with a low percentage of carbon can be made; and, third, that 
sulphur can be readily slagged as calcium sulphide with a charge of 
excess lime. 

THEORY. 

A ferromolybdenum containing 80 per cent molybdenum has a dull 
iron gray color, coarse structure, a high density, and is nonmagnetic. 
It does not break up easily. The 75 per cent alloy is about the same 
as the above, but has a needle structure, and when treated with 
another magnet is so magnetic that it has about three times the 
magnetism of soft steel. 

A commonly used basis for calculating the charge for the reduction 
of ferromolybdenum from molybdenite is the reaction used by 
Becket in his patent.® Carbon is the reducing agent and lime is 
used as a desulphurizing agent. The reaction is as follows: 

2MoS 2 +2CaO+3C=2Mo+2CaS+2CO+CS 2 . 

Pure molybdenite contains 60 per cent molybdenum and 40 per 
cent sulphur. According to the above reaction, 100 parts of molyb¬ 
denum are reduced from 170 parts of molybdenite by 18.8 parts of 
carbon. If the reaction is to be complete, for every 100 parts of 
molybdenum present as the molybdenite, 58 parts of lime are neces¬ 
sary for the slagging of the sulphur. If calcium carbonate instead of 
lime be used, the reaction is: 

2MoS 2 +2CaC0 3 +5C=2Mo+2CaS+CS 2 +6CO. . 

If calcium carbide be used as a reducing agent, the following 
reaction takes place: 

5MoS 2 -)- 2Ca0 2 =5Mo -J- 20aS -}-4CS 2 . 

Becket, in his patent, states that an alloy containing less than 0.2 
per cent carbon can be made by this method. Molybdenum does not 
combine as readily with carbon to form carbides as do some of the 
other metals, such as chromium and tungsten. 

Becket was granted a patent 6 based upon the desulphurizing of 
molybdenite with silicon. The reaction involved is: 

MoS 2 +Si=Mo+SiS 2 

Neumann’s experiments indicate that the use of the latter reaction 
is not very satisfactory. By this method the production of 100 parts 
of molybdenum requires 29 parts of silicon, which would probably 
be used in the form of ferrosilicon, the iron in the ferrosilicon making 
the desired percentage in the ferromolybdenum. 


a U. S. Patent 835052, Nov. 6,1900. 


* U. S. Patent 855157, May 28, 1907. 






150 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

PROCESS OF MANUFACTURE. 

Ferromolybdenum is manufactured commercially in an electric 
furnace of the electrode type operated as a resistance furnace, or in a 
crucible furnace of the resistance type. Comparatively little ferro¬ 
molybdenum is made because of difficulty in getting ores, as satisfac¬ 
tory methods of concentrating molybdenite ores have not as yet been 
fully developed. There are deposits of molybdenite in the United 
States in Maine, Oregon, Colorado, Nevada, and Washington. There 
are also deposits in Canada, Germany, Japan, Mexico, New South 
Wales, New Zealand, Norway, Peru, and Queensland. Queensland 
and New South Wales are the largest producers. Buyers require an 
ore or a concentrate containing 90 to 95 per cent molybdenite, for 
which the price is about $450 per short ton. In commercial manu¬ 
facture, raw or roasted molybdenite, iron turnings, lime, and coke 
or coal are mixed to give a ferromolybdenum of the desired propor¬ 
tions, and the mixture is treated in the electric furnace. The furnaces 
are operated intermittently; that is, one charge is completely dis¬ 
charged before another is added. Analyses of typical electric-furnace 
ferromolybdenum are given in the table following. Ferromolybdenum 
is first made as a high-carbon alloy containing 3 to 4 per cent carbon. 
This is then decarburized with a lime slag or a slag of lime and iron 
oxide. If tire latter is used, the percentage of iron in the alloy is 
increased. 

Analyses of typical ferromolybdenum. 


i 

Analysis No. 1 

2 

3 

4 

Molybdenum. 

Per cent. 
85.8 

10. 963 
3.07 
.11 

Per cent. 
75.0 
18.5 
4.0 
.2 
.1 
. 15 
. 15 
.03 
.03 

Per cent. 
85.2 
14.017 
.45 
.252 

Per cent. 
50.311 
48.92 
.35 
.30 

Iron. 

Carbon. 

Silicon. 

Aluminum. 

Calcium. 




Manganese. 




Sulphur. 

.05 

.007 

.031 

.02 

.030 

.20 

Phosphorus. 



USES. 


Ferromolybdenum in definite proportions is added to steel in the 
open-hearth crucible or in the electric furnace. It gives the steel 
properties similar to those of tungsten steel, but only one-third to 
one-quarter as much is necessary. Molybdenum is added to steel 
that is to be used for such forgings as crank and propeller shafts, for 
gun barrels, wire, boiler plates, armor-piercing shells, motor-car steel, 
magnet steel, and high-speed steel. 

Molybdenum considerably increases the elongation and elastic 
limit of steel. By the*addition of 0.25 per cent of molybdenum the 

































FERRONICKEL. 


151 


elongation has been increased from 4 per cenb up to 45 per cent. The 
addition of small quantities of molybdenum to nickel steels increases 
their resistance to blows without proportionally di min ishing their 
elongation. A nickelchrome molybdenum steel has been used for 
armor plate. 

Tempering has a much more energetic action in molybdenum steel 
than in carbon steels. If sufficient chrome is added to steels con¬ 
taining a high percentage of molybdenum, they lose a large part of 
their electricity, harden in the air, and have the same qualities as 
tungsten high-speed steels. The advantage in using molybdenum 
instead of tungsten in a high-speed steel is that it gives all the desira¬ 
ble qualities to high-speed steel, with the advantage that the carbon 
content is kept below 1 per cent, the hardness and brittleness of tung¬ 
sten high-speed steels being thus avoided. Also, if ferromolybdenum 
could be produced as cheaply as ferrotungsten it would be more 
economical to use because of the decreased amount necessary to give 
the same qualities. 

FERRONICKEL. 

Nickel is usually incorporated in steel by the addition of metallic 
nickel rather than of ferronickel. Most of the ferronickel now used 
occasionally is made in a crucible furnace, fired by coal or gas, rather 
than in the electric furnace, as it is made by simply melting iron and 
nickel in the proper proportions. The metallic nickel used contains 
99 per cent nickel. Ferronickel as supplied contains 25 per cent, 
35 per cent, 50 per cent, 75 per cent, and 85 per cent nickel. The 
impurities in these alloys consist of 0.5 to 1 per cent carbon, 0.2 to 0.3 
per cent silicon, 0.01 to 0.02 per cent sulphur, and 0.2 to 0.3 per cent 
phosphorus. It is claimed that these alloys give a more homogeneous 
mixture of nickel in the steel than is obtained by the use of the ordi¬ 
nary nickel metal. The alloy is malleable, homogeneous, and can be 
readily rolled, drawn, or worked. The ferronickel containing 25 per 
cent nickel is practically nonmagnetic. 

EXPERIMENTS ON THE PRODUCTION OF NATURAL ALLOYS OF 
NICKEL DIRECTLY FROM ORE IN THE ELECTRIC FURNACE. 

EXPERIMENTS AT SAULT STE. MARIE. 

In 1907, during the course of the experiments on the production 
of pig iron in the electric furnace at Sault Ste. Marie, several runs 
were made on the reduction of roasted pyrrhotite with charcoal. 0 

a Haanel, E., Report on the experiments made at Sault Ste. Marie, Ontario, under Government auspices, 
in the smelting of Canadian iron ores by the electrothermic process: Mines Branch, Department of the Inte¬ 
rior, Canada, 1907. 

44713°—Bull. 77—16-11 




152 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


The furnace used in these experiments was similar in general 
design to that shown in figure 38. It took about 4 150 to 175 kilo¬ 
watts. The results of the experiments are given in the table below: 

Results of experiments on the production of ferronickel from roasted pyrrhotite. 


Roasted pyrrhotite. 

Charcoal. 

Constit¬ 

uent. 

Per cent. 

Constituent. 

Per cent. 

Si0 2 . 

10.96 
f 65.43 

\ (45.8 Fe) 
3.31 
3.92 

3.53 
1.56 
.016 
.41 
2.23 

Moisture. 

2.20 
20.60 
74.40 
2. 80 

Fe 2 03.... 

A1 2 0 3 .... 
CaO. 

Volatile matter... 

Fixed carbon. 

Ash. 


MgO. 

S. 

P. 

Cr. 

Ni. 



Limestone 


Charge. 

Consticuent. 

Per cent. 

Constitu¬ 

ent. 

Pounds. 

Si0 2 . 

1.71 

Ore. 

14,500 

Fe 2 03+Al 2 03. 

.81 

Charcoal.. 

4,050 

CaC0 3 . 

92.85 

Limestone 

3,185 

MgC0 3 . 

4.40 

Quartz.... 

40 

P. 

.004 

Fluorspar. 

25 

s. 

.052 




Average analysis of ferronickel. 


Average analysis of slag. 


Constituent. 

Per cent. 

1 

Constituent. 

Per cent. 

Nickel. 

4.01 

Si0 2 . 

21.43 

Copper.? 

.71 

A1 2 0 3 . 

11.60 

Carbon. 

3.19 

CaO. 

49.63 

Manganese. 

. 10 

MgO. 

8.78 

Silicon. 

4.90 

MhO. 

. 10 

Phosphorus. 

.043 

FeO.. 

.28 

Sulphur. 

.005 

CaO... 

.015 



NiO. 

.018 



P 2 O 5 . 

4.46 



S. 

.02 


Length of ran, horn's and minutes 

Mean volts on furnace. 

Mean amperes on furnace. 

Power factor. 

Kilowatts. 

Ferronickel tapped, pounds. 

Kilowatt-hours per pound. 

Kilowatt-years per ton. 


56 20 
36.12 
5,000 
.919 
165.9 
7,336 
1.27 
.29 


The furnace was later used in the production of ferronickel. The 
results of the work done later is given in the report by the metal¬ 
lurgist of the company that purchased the furnace. The ore and 
raw materials were of about the composition given for those sub¬ 
stances in the table above. Four hundred pounds of briquetted 
roasted ore, 140 to 150 pounds of limestone, and 120 pounds of char¬ 
coal were the proportions used. During four months of operation, 154 
short tons of ferronickel of approximately the composition given was 
produced, with a power consumption of 0.34 kilowatt-year per ton. 
The electrode consumption was 40 pounds of amorphous carbon per 
ton of ferronickel. To produce a product containing 4 per cent nickel, 
2.75 per cent silicon, 0.8 per cent copper, 0.01 per cent sulphur, and 
0.03 per cent phosphorus, on the average 2 tons of roasted pyrrhotite 
(2 per cent sulphur), 1,500 pounds of limestone, and 1,200 pounds of 
charcoal were used. 













































































FERRONICKEL. 


153 


The results of the operation of the furnace show the possibility of 
producing a low-grade ferronickel directly from roasted ore in the 
electric furnace. Owing to the low percentage of nickel in the ore a 
high percentage of nickel could not be concentrated in the metal. 
There was difficulty in selling the product, so that after a short period 
of operation the work was discontinued. The product was not pure 
enough or high enough grade for steel manufacture. 

4 

EXPERIMENTS AT PLANT IN NORTH CAROLINA. 

A plant was erected at Webster, Jackson County, N. C., where 
experiments were conducted on the reduction of garnerite in the 
electric furnace with coke as a reducing agent.® The furnace used 
was similar to the one shown in figure 41. The ores used were gar¬ 
nerite, containing 7.3 per cent Ni., 37.5 per cent Si0 2 , 29 per cent Al, 
1.8 per cent Fe, 10 per cent Mg, 0.1 per cent CO, and 11.9 per cent 
H 2 0, and dunite, containing 1.7 per cent Ni, 41.8 per cent Si0 2 , 6.7 
per cent Al, 8.3 per cent Fe, 28.2 per cent Mg, 0.02 per cent CO, and 
10.9 per cent H 2 0. About 10 per cent of coke was used. The prod¬ 
uct made was a nickel silicide containing 10 to 30 per cent nickel, 20 
to 30 per cent silicon, 40 to 50 per cent iron, 5 to 10 per cent Al, 

3 to 5 per cent Cr, and 3 to 4 per cent of carbon, magnesium sulphur, 
and phosphorus. The average power on the furnace was 200 kilo- ' 
watts. About 7,800 pounds of ore was smelted per 24 hours. b In a 
typical run 6.3 kilowatt-hours was used per pound of nickel silicide 
produced. The silicide contained 11.9 per cent nickel. The plant 
is no longer in operation. Power was very expensive at the point of 
erection of the experimental plant. It was stated to cost $200 per 
kilowatt-year. 

EXPERIMENTS OF STEPHAN. 

In 1903, at the works of the Societe Anonyme Electrometallurgique 
Procedes Paul Girod, Stephan worked on the production of a nickel 
silicide from a silicon ore of nickel. 0 The product contained 30 per 
cent nickel and 47.20 per cent silicon. In 1911, experiments were 
performed at the same works in an attempt to make a ferronickel 
containing 3 to 5 per cent silicon. 

The furnace used was of the type shown in figure 43. It was of 220 
kilowatts capacity and treated 8 tons of ore, with the production of 
770 pounds of metal, in 24 hours. The power consumption was 1,760 
kilowatt-hours per ton of ore treated, or 6.86 kilowatt-hours per 
pound of alloy obtained. In practice it is believed the power con- 

a Anon., Electric smelting of nickel ore: Met. and Chem. Eng., vol. 8,1910, p. 277. 

b Morrison, W. L., Electric-furnace treatment of nickel ore and the development of a commercial process: 
Trans. Am. Electrochem. Soc., vol. 20,1911, p. 315; Met. and Chem. Eng., vol. 4,1911, p. 546. 

c Stephan, M., Einiges liber die Erzengang von Metallen im elektrischen Ofen: Metal und Erz, vol. 1, 

1912, p. 11. 



154 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

sumption could be reduced to 1,200 kilowatt-hours per ton of ore, or, 
on the basis of the same percentage extraction, to 4.69 kilowatt-hours 
per pound of alloy. The results of the experiment are shown below: 


Results of Stephan's experiments on the production of ferronickel. 


Ore. 

Ferronickel. 

Slag. 

Constituent. 

Per cent. 

Constituent. 

Per cent. 

Constitu¬ 

ent. 

Per cent. 

NiO. 

8.33 

Nickel. 

41.50 

Ni0 2 . 

0.31 

Si0 2 . 

28.58 

Iron. 

51.6 

Si0 2 ~. 

53.98 


14.61 

Silicon . 

4.33 

FeO". 

1.56 

MgO". 

20. 65 

Silicide. 

Trace. 




2.33 

Aluminum. 

.81 



H 2 0 ’. 

12.32 

Carbon. 

1.34 



Moisture. 

12.54 

Sulphur. 

.04 










FERROPHOSPHORUS. 


Ferrophosphorus is made in the electric furnace from apatite or 
other phosphorus-bearing mineral. It is used in the open hearth for 
enriching the slag so as to get phosphorus into the steel, as steel for 
sheet purposes, particularly tin plates, can be rolled more satisfacto¬ 
rily if it contains phosphorus. Two grades of ferrophosphorus are 
used. One contains 16 to 20 per cent phosphorus and has the follow¬ 
ing analysis: 17.5 per cent phosphorus, 76.2 per cent iron, 0.42 per 
cent silicon, 0.27 percent carbon, and 5.75 per cent manganese. The 
other grade contains 20 to 25 per cent phosphorus and has 24.0 per 
cent phosphorus, 73.3 per cent iron, 2.47 per cent silicon, 0.03 per cent 
carbon, 0.08 per cent sulphur, and 0.10 per cent manganese. Alloys 
containing phosphorus and manganese are also made. Some ferro¬ 
phosphorus is made in Canada in the electric furnace, but most of it 
comes from Europe, except what is produced by a blast furnace in 
Tennessee. 

FERRO SILICON. 

HISTORY. 

Ferrosilicon is the most extensively used of all the ferro-alloys 
produced in the electric furnace. If all ferro-alloys be considered, it is 
second only to ferromanganese in amount consumed. Ferrosilicon was 
first prepared in 1810 by Berzelius °, who, with a mixture of iron shav¬ 
ings, silica, and carbon, obtained an alloy containing 9 per cent silicon. 
In 1811, Strohmayer ° repeated the experiments of Berzelius and pre¬ 
pared a series of alloys containing 2.2 to 9.3 per cent silicon. Yalten 6 
made ferrosilicon at Terre-Noire in 1872 by the reduction of iron oxide 
and silica in a crucible with carbon. There was 10 to 12 per cent sili- 


o Conrad, W., and Pick, W., Die Herstellung yon Hochprozentigem Ferrosilizium im elektrischen Ofen, 
1909. Revue de M6tallurgie, vol. 9, 1912, p. 362. 
b Guillet, L., Etude industrie) des alliages mdtallique. 







































FERROSILICON. 


155 


con in the product. Using iron turnings, silica, and carbon, he ob¬ 
tained an alloy containing 22 per cent silicon. In 1875 Pourcel made 
15 per cent ferrosilicon in the blast furnace at Terre-Noire. Silico- 
spiegel was made at the same time in the blast furnace of Pourcel. 
From that time on, the manufacture of ferrosilicon in the blast furnace 
became firmly established. Moissan® in his electric furnace work 
made some ferrosilicon and silicides. The first company to take up 
the manufacture of ferrosilicon in the electric furnace was a company 
in West Virginia operating under the Chalmot patents 6 in 1898. 
Thus the manufacture of this important alloy in the electric furnace 
was begun in the United States, but to-day comparatively little is 
produced in this country. Blast-furnace ferrosilicon had been manu¬ 
factured for many years previous to this in the United States. In 
1899 the carbide industry in Europe began to collapse, and the manu¬ 
facture of ferro-alloys was commenced. The first product made was 
ferrosilicon, the production of which was commenced in 1899 at Bozel, 
France, under the patents of Rothenau. 0 This was followed by a 
plant at Meran, Switzerland, in 1900, a plant at Giffre, Switzerland, 
in 1901, and plants at Matrei, Austria, and at Notre Dome de Briar^on, 
Ugine, Livet, and Albertville, France, in 1902. There are to-day 
many other plants in France, Germany, Switzerland, Austria, Norway, 
and Sweden. In the United States there is but one producer, a com¬ 
pany that operates an old aluminum plant at Kanawha Falls, W. Va., 
and also one at Niagara Falls, N. Y. It is said that not all of the ferro¬ 
silicon sold by this company is manufactured in this country, some 
being imported. At Welland, Ontario, Canada, there is a ferrosilicon 
works producing about 4,000 tons yearly. The product contains 50 
per cent of silicon. Some of it is exported to the United States. 

THEORY. 

SILICIDES OF IRON. 

A silicide of iron in the proportion 87.28 per cent iron and 11.01 per 
cent silicon was found in a meteor by Shepard in 1859. Carnot and 
Goutal d isolated the silicide (FeMn) 3 Si by treatment of a silicon 
spiegel with sulphuric acid. This corresponds in silicospiegel to the 
silicide Fe 3 Si, 85.714 per cent iron and 14.286 per cent silicon, that 
possibly exists in ferrosilicon. Naske 6 tried to obtain pure Fe 3 Si by 
treating a ferrosilicon containing 13.19 per cent silicon with ammo- 
niacal copper chloride, but was unsuccessful. By treating a 10 per 

a Moissan, H., Action du silicum sur le fer, le chrome et l’argent: Compt. Rend., vol. 121,1895 p. 621. 

b U. S. patents Nos. 602975 and 602976, Apr. 26, 1898. 

c Carnot, and Goutal, Recherches sur l’etat ou se trouvent le silicium et le chrome dans les produits 
siderurgiques: Compt. Rend., vol. 126, 1898, p. 1240. 

d Carnot, and Goutal, Loc. cit. 

e Conrad, W., and Pick, W., Die Herstellung von Hochprozentigem Ferrosilizium in elektrischen Ofen, 
1909. Rev. de Mdtallurgie, vol. 9,1912, p. 362. 




156 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


cent ferrosilicon with sulphur, he obtained a magnetic product which 
resembled a mixture of FeS and Fe 3 Si. Although the silicide 
Fe 3 Si has not been actually isolated, its existence seems probable by 
analogy with cemantite Fe 3 C and (FeMn) 3 C. Fe 3 Si is decomposed 
after a long time by dilute sulphuric acid, and is dissolved by hydro¬ 
chloric acid from all silicides containing less than 20 per cent silicon. 
It is not attacked by dilute nitric acid. 

The silicide Fe 2 Si, 80 per cent iron and 20 per cent silicon, has been 
isolated from commercial products by Carnot and Goutal, 0 by 
Osmond, 5 and by Lebeau. c Carnot treated ferrosilicon with dilute 
nitric acid and ammoniacal copper chloride and Goutal treated it 
with warm dilute nitric acid. Hahn obtained Fe 2 Si by synthesis, 
fusing iron chloride, sodium chloride, amorphous silicon, sodium, ancj 
fluorspar. In the electric furnace Moissan d heated iron oxide and 
crystallized silicon to obtain Fe 2 Si. Lebeau obtained it by heating 
a mixture of iron and cuprosilicon. 

Fe 3 Si forms small prismatic crystals of metallic appearance. It is 
magnetic and has a specific weight of 7. It is not attacked by either 
dilute or concentrated nitric acid. It is dissolved easily by hydro¬ 
chloric acid, with more difficulty by aqua regia, and completely by 
hydrofluoric acid. In alkaline solution it is dissolved completely only 
in hot concentrated solution. 

The silicide Fe 3 Si 2 , which is found frequently in industrial products 
bearing 25 to 28 per cent silicon, contains 75 per cent iron and 25 per 
cent silicon. It forms octahedral crystals and has a specific gravity 
of 6.7. It is as magnetic as Fe 3 Si and Fe 2 Si. It is stable in the pres¬ 
ence of all acids. Chlorine or bromine attacks it when at a red heat. 
According to Gin, it is decomposed at a high temperature into Fe 2 Si 
and Si. 

The best known silicide of iron is FeSi, 66.67 per cent iron and 33.33 
per cent silicon. This alloy was prepared by synthesis by Fremy, 
through the action of silicon chloride upon iron, and by Lebeau 
through the action of cuprosilicon on iron. Lebeau also isolated 
FeSi from ferrosilicon containing 35 per cent silicon. FeSi crystal¬ 
lizes in tetrahedral needles. Its specific weight is 6.17, and its hard¬ 
ness about 7. When cold it is attacked by fluorine; at a dull red heat 
it is attacked by bromine and chlorine, by an alkaline fusion, by hy¬ 
drofluoric acid, or by a mixture of hydrofluoric and nitric acids. 

The silicide FeSi 2 , 50 per cent each of iron and silicon, has been 
little studied. It has been prepared by Hahn and Lebeau by syn- 

a Carnot, and Goutal, Researches sur l’etat ou se trouvent le silicium et le chrome dans les produits 
siderurgiques: Comp. Rend., vol. 126,1898, p. 1240. 

b Osmond, F., Recherches calorimetriques sur l’<$tat du silicium et de l’aluminium dans les fers 
fondus: Compt. Rend., vol. 113,1891, p. 474. 

c Conrad, W., and Pick, W., Die Herstellung von Hochprozentigem Ferrosilizium im elektrischen Ofen, 
1909. Rev. de Metallurgie, vol. 9,1912, p. 362. 

d Moissan, H., Action du silicium sur le fer, le chrome et l’argent: Compt. Rend., vol. 121, 1895, p. 621. 




FERROSILICON. 


157 


the tic methods. Chalmot treated 39 to 50 per cent ferrosilicon with 
cold dilute hydrofluoric acid to obtain it. Its specific weight is 5.4 
and its hardness 4 to 5. Hydrofluoric attacks it only in concentrated 
solution, and the other acids have no effect upon it. 

The silicide FeSi 3 , 40 per cent iron and 60 per cent silicon, is also 
little known. Naske obtained it from a ferrosilicon by treatment with 
hydrofluoric acid. It was in the form of a crystalline powder, which 
was insoluble in all solvents and attacked with difficulty by carbonate 
fusion. Pick claims that this silicide exists only in ferrosilicon con¬ 
taining a high percentage of silicon. 



Figure 53. —Cooling curves of the iron-silicon system. 


Tamman a and Giirtler have obtained the cooling curves of the iron- 
silicon system (fig. 53). They show the existence of only two sili- 
cides, Fe 2 Si and FeSi, but from work of others it seems that there 
surely exist three, Fe 2 Si, FeSi, and FeSi 2 , and perhaps two others, 
Fe 3 Si and FeSi 3 . 

The resistance of silicides of iron to acids increases and the specific 
weight and magnetic power decrease when the silicon content in¬ 
creases. They all have a good electrical conductivity and are disin¬ 
tegrated by carbonate fusion more or less easily according to their 
silicon content. 

a Conrad, W.,and Fick, W., Die Herstellung von Hochprozentigem Ferrosilizium im elektrischen Ofen, 
1909. Rev. de Metallurgie, vol. 9,1912, p. 362. 


























158 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

PROPERTIES OF FERRO SILICON. 0 

Ferrosilicon always has a crystalline appearance. If its silicon con¬ 
tent is less than 20 per cent it is dull, shows a fine crystallization, and 
resembles white iron. With a silicon content of 20 to 30 per cent the 
crystals become more brilliant and show a slaty crystallization. 
With a silicon content of 50 per cent or more, the crystallization dis¬ 
appears and is replaced by a fine texture resembling more and more 
silicon. It is not difficult to judge the percentage of silicon by the 
eye, according to the texture and the color of the fractured surface. 
As the percentage of silicon increases to more than 50 per cent, the 
ferrosilicon takes on a bluish color. 

The various grades of commercial ferrosilicon are substantially 
binary alloys. Two compounds, Fe 2 Si and FeSi, exist. The micro¬ 
structure indicates two eutectics, one containing 21.6 per cent silicon 
(Fe 2 Si and FeSi) and the other containing 60 per cent silicon 
(FeSi and Si). With a silicon content of less than 20 per cent the 
alioys consist of solid solutions of Fe and Fe 2 Si, which are hard, firm 
masses giving off little or no gas. Alloys with a silicon content of 
20 to 21.6 per cent silicon consist of primary crystals of Fe 2 Si in a 
ground of a eutectic composed of Fe 2 Si and FeSi. These alloys are 
more brittle than the lower grades. With a silicon content of 21.6 
to 33.3 per cent, the structure shows FeSi surrounded by the eutectic 
Fe 2 Si and FeSi. With a silicon content of 33.3 to 60 per cent there 
are crystals of FeSi in the eutectic FeSi and Si. With more than 60 
per cent of silicon there exist silicon crystals in a field of the eutectic 
FeSi and Si. 

With a silicon content of 30 per cent or less, ferrosilicon is hard and 
has no tendency to disintegrate spontaneously. Samples containing 
30 to 65 per cent silicon show a decided tendency to spontaneous 
disintegration. They crumble on keeping, and some of them actually 
fall to powder after a few weeks. This spontaneous disintegration 
is usually accompanied by the evolution of bad-smelling and poisonous 
gases. Although samples with a silicon content of 70 to 96 per cent 
are somewhat brittle, they are not so easily broken and reduced to 
powder as those containing between 30 and 65 per cent silicon, and 
they do not show a tendency to disintegrate spontaneously. 

The specific gravity decreases as the percentage of silicon increases, 
because the specific gravity of pure iron is 7.8, whereas that of pure 
silicon is 2.49. In figure 54 a curve representing the results of 
determinations of the specific gravity of various samples of commercial 
ferrosilicon, made by Dr. Hahe, of the British Local Government 
Board, is shown in comparison with the theoretical curve representing 
the calculated specific gravities for all percentages on the assumption 


a Copeman, S. M., Bennett, S. R., and Hahe, H. W., Yellow book of British Local Government Board 
on the Manufacture, Uses, and Transport of Ferrosilicon, 1910: Met. and Chem. Eng., vol. 8,1910, p. 133. 



FERROSILICON. 


159 


that mixtures of iron and silicon are formed without change of volume. 
A comparison of the two curves shows that the assumption is not 
correct, that the specific gravities are partly above and partly below 
the theoretical curve, and that contraction of volume occurs in the 
alloys containing 60 per cent or less of silicon, and expansion of vol¬ 
ume in alloys containing more than 60 but less than 96 per cent sili¬ 
con, presumably owing to the presence of definite silicides of iron in 
the alloys. 

According to the diagram of Tamman and Gurtler (fig. 53), the 
fusing point of 25 and 50 per cent ferrosilicon is 1,360° C. The melting 
point of silica is 1,425° C., and of iron 1,540° C. 

The chemical purity of the product decreases slightly with de¬ 
crease in the silicon content. Compared with the impurities of the 



Figure 54.—Specific gravity curves of ferrosilicon samples containing varying percentages of ferrosilicon. 
Irregular line represents results of actual determinations. Uniform curve represents calculations based 
on assumption that mixtures of iron and silicon are formed without change of volume. 

\ 

blast-furnace alloys, the impurities in electric-furnace ferrosilicon are 
low. The calcium content in the 25 per cent grade is about 0.5 per 
cent, and increases to 0.7 to 1 per cent for 90 per cent ferrosilicon. 
The magnesium content varies from 0.10 per cent in the 25 per cent 
grade to 0.3 per cent in the 90 per cent grade. The average aluminum 
content in all grades is between 0.1 and 0.15 per cent. In the blast¬ 
furnace ferrosilicon the percentage of carbon is 1 to 1.5 per cent. 
This diminishes with increase in the silicon content, so that in the 25 
per cent grade there is about 0.35 per cent carbon, and in the 90 per 
cent grade the carbon content is as low as 0.2 per cent. The phos¬ 
phorus content is generally less than 0.10 per cent, the sulphur 
content less than 0.05 per cent, and the manganese content less than 
0.4 per cent. 





































160 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

DISINTEGRATION AND EVOLUTION OF GAS FROM FERROSILICON. 

As has been stated, a ferrosilicon containing between 30 and 65 per 
cent silicon has a tendency to disintegrate. It is not known whether 
this property is inherent in these grades, or whether it is due to chemi¬ 
cal or physical conditions. The main impurity that might cause dis¬ 
integration is calcium. If the calcium were present in the state of a 
silicide, the alloy would be stable, but if the calcium were present 
as calcium carbide, the alloy would be very unstable. The presence 
in ferrosilicon of calcium as calcium carbide might be due to the 
manufacture of ferrosilicon in an old carbide furnace. In a new fur¬ 
nace there should be no contamination by carbide. 

It has been noticed that disintegration occurs in spots. In a mass 
of ferrosilicon of uniform composition, part will stay solid and part 
break up. Coating the product with paraffin has been tried, but 
is no longer believed to be efficacious, as it affects only the surface. 
Some persons believe that disintegration is affected by the tempera¬ 
ture of pouring and the density of the current of electricity in the 
electrodes. When the temperature is high and the amount of cur¬ 
rent great, the product seems to be more subject to disintegration. 
It is possible that there is a phenomenon analogous to the allotropic 
changes of certain elements, such as sulphur. The solid parts have a 
homogeneous structure and grain, whereas the substance affected by 
disintegration consists of crystals surrounded by a powder. 

There is evolution of explosive and poisonous gases from these 
grades of ferrosilicon when the alloy is in moist air and when there is 
friction between the particles of the alloy as in transportation. Dupre 
and Lloyd a attribute the explosions to acetylene gas made to ignite 
by the presence of small quantities of phosphide of hydrogen (PH 3 ), 
and when this is not present by sparks from attrition of particles 
of ferrosilicon. Wilson a found silicide of hydrogen. Ashenary ° 
believed the gas to be hydrogen. Most investigators believe the poi¬ 
sonous gas to be PH 3 , as phosphide of calcium and phosphide of iron 
are not decomposed by water. 

In his report to the British local government board, Halie states 
that he found pliosphoretted hydrogen (PH 3 ) and arseniuretted 
hydrogen (AsPI 3 ). He did not find in the samples tested any sili- 
ciuretted hydrogen (SiH 4 ) nor acetylene (C 2 H 2 ), although others 
report those gases present as in ferrosilicon. It is probable that the 
poisonous emanations are pliosphoretted hydrogen and arseniuretted 
hydrogen evolved by the action of water. 

The formation of these gases is due to the presence of small quan¬ 
tities of calcium phosphate [Ca 3 (P0 4 ) 2 ] and arsenic in the raw mate- 


a Conrad, W., and Pick, W., Die Herstellung von Hockprozentigem Ferrosilizium iin elektrischen Ofen, 
1909. Rev. de Metallurgie, vol. 9, 1912, p. 362. 




FERROSILICON. 


161 


rials. Calcium phosphate occurs in coal and quartz. In itself it is 
harmless. It is insoluble in water and is common in nature. In the 
electric furnace, in the presence of carbon, it is reduced to calcium 
phosphide (Ca 3 P 2 ). The calcium phosphide remains in the ferro- 
silicon and in contact with water in moist air is decomposed with 
evolution of phosplioretted hydrogen (PH 3 ), which is very poisonous. 
Arsenic occurs in nature closely associated with phosphorus, and 
finds its way into the ferrosilicon as calcium arsenide, which is 
decomposed by water or moist air, with the formation of arseniuretted 
hydrogen (AsH 3 ), also a poisonous gas. 

These gases are evolved only by the grades of ferrosilicon that 
disintegrate easily—containing 30 to 65 per cent silicon. The British 
Government board classed as dangerous all grades that contained 
between 30 and 70 per cent silicon. 

REDUCTION WITH CARBON. 

Ferrosilicon is made commercially in two ways only—by the 
reduction of silica and iron ore with carbon or by the reduction of 
silica with carbon, the iron being added as iron turnings, which are 
simply melted. The utilization of siliceous and ferruginous slags 
has been proposed, but has not been adopted commercially, and 
experiments of the writer indicate that it does not seem practicable. 

Silica is reduced by solid carbon at a temperature of 1,485° C. 
The reduction point of silicon is lowered if there is iron present in 
the charge to combine with the silica.® With a charge composed 
of 20 parts of silica, 30 parts of iron, and 8 parts of carbon the 
temperature of reduction was lowered to 1,200° C. in experiments 
performed by Greenwood. In commercial practice the presence 
of iron to lower the reduction temperature is important, as is shown 
by the fact that furnaces working upon a low-silicon product, with 
a large charge of iron operate better than when treating a high- 
silica product with a low iron charge. 

Reduction takes place according to the formula: 

Si0 2 +2C=Si+2C0. 

Thus, the reduction of 100 parts of silicon from 214 parts of silica 
requires 86 parts of carbon. The reduction of iron oxide is generally 
by the solid carbon only, according to reaction: 

Fe 2 0 3 +3C=2Fe+3CO. 

By this formula for the reduction of 100 parts of iron from 143 
parts of hematite 32 parts of carbon is necessary. In the usual 

O Greenwood, H. C., Sluele, R. E., Prinz, J. N., Reduction of refractory oxides, production of ferro¬ 
alloys and formation of carbides. Trans. Chem. Soc. (England), vol. 9h, 1908, p. 14S4. Electrochom. 
and Met. Ind., vol. 7, 1909, p. 119. 






162 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


ferrosilicon furnace there is no shaft, so that reduction results mainly 
in the formation of gas, the greater part of which is carbon monoxide, 
as shown in the above formula. 

In the calculation of theoretical power consumption the following 


constants are used: a 

Reduction or oxidation. Calories 

absorbed. 

1 kg. Fe from Fe 2 0 3 . 1, 746 

1 kg. Si from Si0 2 . 6, 428 

lkg. C to CO. 2,430 


The specific heat of iron for temperatures ranging from 0° to 
1,400° C. is taken as the average 0.20; of silicon for temperatures 
ranging from 0° to 1,400° C., 0.25; and of carbon for a similar range,. 
0.50. 

Theoretically the energy necessary for the reduction of 1 kg. (2.2 
pounds) of silicon from silica is the result of dividing 6,428 by 857, 
or 7.5 kilowatt-hours per kilogram (3.4 kilowatt-hours per pound). 
The amount of energy necessary to reduce a long ton of pure silicon 
would then be 7,600 kilowatt-hours, or 0.87 kilowatt-year, per ton. 


PRODUCTION FROM IRON ORE OF FERROSILICON CONTAINING 

30 PER CENT SILICON. 

In the calculations following, relative to producing ferrosilicon 
containing 30 per cent silicon from iron ore, the assumptions made 
are: First, that the iron of the alloy is to be reduced from a pure 
hematite ore 70 per cent iron; second, that the ferrosilicon is to con¬ 
tain 30 per cent iron and 70 per cent silicon; third, that the silicon 
is to be from a pure quartz containing 46.7 per cent silicon; and, 
fourth, that the reduction is to take place according to the given 
reactions. The calculations follow: 

Calories 

Reduction. required. 

700 kg. Fe from Fe 2 0 3 .700X1,746. 1, 222, 200 

300 kg. Si from Si0 2 .300X6,428. 1, 928, 400 

Heating. 

700 kg. Fe to 1,400° C .700X1,400X0.2. 196, 000 

300 kg. Si to 1,400° C .300X1,400X0.25.... 105,000 

482 kg. C to 1,400° C .482X1,400X0.5. 337,400 


Total. 3,789,000 

Amount of heat supplied: 

By combustion of 482 kg. C.482X2,430_1,171, 260 

By the electric current. 2, 617, 740 


Total. 3,789,000 

Therefore, the theoretical amount of electrical energy necessary 
for the production of 30 per cent ferrosilicon from iron ore and quartz 
is the result of dividing 2,617,740 by 857, or 3,054 kilowatt-hours per 
metric ton, or, in terms of the long ton, 3,109 kilowatt-hours, or 
0.35 kilowatt-year per long ton. 


a Richards, J. W., Metallurgical calculations, 1908, vol. 1. 





















FERROSILICON. 


163 


PRODUCTION OF FERROSILICON CONTAINING 30 PER CENT SILICON 

FROM IRON TURNINGS. 


In the calculations following, relative to producing ferrosilicon con¬ 
taining 30 per cent silicon from iron turnings, the assumptions made 
in the ore are as follows, the same as for the production of 30 per cent 
ferrosilicon using iron ore, except that in this case wrought iron or 
steel turnings are the source of iron: 

Calories 

Reduction. required. 

300 kg. Si from Si0 2 . 300X6,428. 1, 928, 400 

Heating. 


700 kg. Fe to 1,400° C. 700X1,400X0.2. 196, 000 

300 kg. Si to 1,400° C. 300X1,400X0.25_ 105, 000 

258 kg. C to 1,400° C. 258X1,400X0.5. 180, 600 


Total. 2,410,000 

Amount of heat supplied: 

By combustion of 258 kg. C.258X2,430_ 626, 940 

By the electric current. 1, 783, 060 


Total. 2,410,000 

Therefore the theoretical amount of electrical energy necessary 
for the production of 30 per cent ferrosilicon from iron turnings and 
quartz is the result of dividing 1,783,060 by 857, or 2,080 kilowatt- 
hours per metric ton, or 2,116 kilowatt-hours (0.24 kilowatt-year) 
per long ton. 

From these figures it is evident that the production of 30 per cent 
ferrosilicon in the electric furnace when iron turnings are used requires 
only 68 per cent of the energy necessary with the use of iron ore. 


FIFTY PER CENT FERROSILICON. 

Analogous to the case of a 30 per cent ferrosilicon, with a 50 per 
cent product the power consumption with iron ore is 3,945 kilowatt- 
hours per metric ton, or 4,010 kilowatt-hours (0.46 kilowatt-year) per 
long ton. If iron turnings are used instead of iron ore the power 
consumption per ton of 50 per cent ferrosilicon made is 3,245 kilowatt- 
hours per metric ton, or 3,300 kilowatt-hours (0.38 kilowatt year) per 
long ton. 

In making 50 per cent ferrosilicon, the saving in energy is not so 
great by using iron turnings instead of iron ore as in making the 30 
per cent product because of the smaller amount of iron necessary in 
the charge. In making the 50 per cent alloy the energy consumption 
with turnings is 82 per cent of that with iron ore. 

MANUFACTURE OF FERROSILICON IN THE BLAST FURNACE. 

Ferrosilicon of less than 20 per cent silicon is made in the blast 
furnace, whereas the electric furnace is used for all the grades con¬ 
taining a higher percentage. The grades made in the blast furnace 















164 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

contain 10 to 20 per cent silicon, most of them containing less than 15 
per cent silicon. Higher grades can not be produced in the blast 
furnace because of the impossibility of obtaining a high enough tem¬ 
perature. The wear on the furnace lining is great, and in order to 
maintain the high temperature necessary, a large quantity of coke 
is employed. As in the electric furnace, the silicon is reduced by 
solid carbon. Reduction is said to be more easy if the slag is low in 
lime and high in alumina—probably because the silicon does not have 
as strong an affinity for alumina as for lime. The charge used in the 
blast furnace may consist of siliceous iron ore, hammer scale, and 
coke, a hot blast being used. Gin gives as a charge: turnings 1,000 
parts, quartz 410 parts, and coke 940 parts.® 

In small furnaces the production is 30 to 40 tons per day, and 
with the large furnaces 80 to 100 tons per day. The blast-furnace 
operation of making ferrosilicon is similar to making pig iron, except 
that, owing to the highly siliceous slags, the steady operation of the 
furnace is more difficult. A small amount of blast-furnace ferrosilicon 
is imported, but most of it is produced here. 

MANUFACTURE OF FERROSILICON IN THE ELECTRIC FURNACE. 

RAW MATERIALS USED. 

There are two general kinds of charge used in the manufacture of 
ferrosilicon in the electric furnace. The charge may consist of 
wrought iron, cast iron or steel turnings, quartz or sand, and charcoal, 
coal, or coke; or siliceous iron ore, quartz or sand, and charcoal, coal, 
or coke may be used. The choice of the source of iron depends chiefly 
on the material available. Iron in the form of turnings of some sort 
is more commonly used than iron ore, because, as has already been 
mentioned, it consumes much less power—68 per cent of the amount 
used for a 30 per cent alloy with iron ore, and 82 per cent for the 50 
per cent product. The operation of a ferrosilicon furnace operating 
on turnings is much steadier and requires less attention because there 
is not as much slag formed as in the ore process. The purer the raw 
materials the purer is the product obtained. For this reason wrought 
iron or steel turnings are preferable to cast-iron borings and are used 
by most works. At the Girod plant, at Ugine, the average composi¬ 
tion of the iron turnings used is 0.4 to 0.5 per cent carbon, 0.15 to 0.25 
per cent silicon, 0.5 to 0.7 per cent manganese, 0.6 to 0.9 per cent 
sulphur, and 0.08 to 0.10 per cent phosphorus. Cast-iron turnings 
contain as high as 0.5 to 0.8 per cent phosphorus. At works at 
Bozel, France, steel or wrought-iron turnings containing less than 0.3 
per cent phosphorus are used. Another French company, at Livet, 
uses steel turnings containing less than 0.10 per cent phosphorus. 


a Conrad, W., and Pick, W., Die Herstellung von Hochprozentigem Ferrosilizium im elektrischen Ofen, 
1909. Rev. de Metallurgie, vol. 9, 1912 p. 352. 




FERROSILICON. 


165 


The St. Marcel, France, works of the Societe d’Industrie Electro- 
Chimiques La Voltes use steel shavings for 30 per cent ferrosilicon, and 
iron ore 95 per cent Fe 2 0 3 for the 50 per cent grade. At Kanawha 
Falls, W. Va., iron ore is used in the production of 30 per cent ferro¬ 
silicon.® The ore contains 62.34 per cent iron, 7.93 per cent Si0 2 , 
0.09 per cent MgO, 0.72 per cent CaO, 0.4 per cent phosphorus, and a 
trace of sulphur. Gin in some experiments used a highly siliceous 6 
iron ore containing 59.2 per cent Fe 2 0 3 , 2.1 per cent MnO, 24.6 per 
cent Si0 2 in producing a 50 per cent ferrosilicon 6 

For the supplying of silicon in the charge, quartzite is preferable to 
sand because it is more nearly pure, and hence does not cause the 
formation of as much slag, which clogs the furnace. Also, the fine 
state of the sand seems to cause less regular operation of the furnace. 
The quartzite is usually crushed to about 2-inch size. At the Bozel 
plant mentioned above, the quartzite charged contains 95 per cent 
Si0 2 , 4 per cent A1 2 0 3 , and traces of calcium and phosphorus. The 
Girod works use quartzite containing 92 per cent Si0 2 and traces of 
phosphorus and sulphur. At St. Marcel the quartzite has 98 per cent 
Si0 2 , and a trace of MgO. 

Whether charcoal, coke, or coal is used depends largely upon the 
cost of those materials in the district where a given plant is located. 
As the materials are used only as reducing agents and as, because of 
the absence of a shaft, no strength is necessary to support the charge 
in the ferrosilicon furnaces, the cheapest reducing material available 
is used. In France the works are all situated in the mountain dis¬ 
tricts where transportation costs are high, so that the local anthracite 
coal is largely employed. Most of such coal is rather high in ash, and 
when grades of ferrosilicon containing 75 per cent or more silicon are 
being manufactured it is customary to employ charcoal to avoid slag 
in the furnace. The slag increases the difficulties of operation con¬ 
siderably in the production of high-grade ferrosilicon and also increases 
the furnace impurities that would pass into the product. At the 
Girod plant in Ugine, coal guaranteed not to average more than 8 per 
cent ash or more than 0.005 per cent phosphorus or sulphur is used. 
The St. Marcel works employ gas coke for the production of 50 per cent 
grades, and a cheaper anthracite coal for the 25 per cent alloy or other 
low grades. A French company at Li vet uses anthracite coal con¬ 
taining 7 per cent ash, 0.013 per cent phosphorus, 0.41 per cent sul¬ 
phur, and no arsenic. At Bozel for the lower percentage alloys—50 
per cent or less—anthracite coal containing 20 per cent ash is charged, 
but in the manufacture of the 80 per cent grade, charcoal is employed. 
In Norway and Sweden, where most of the ferrosilicon works are on 
tidewater or on a canal, anthracite coal of a high grade is generally used. 


a Schoel, G. P., Manufacture of ferro-alloys in the electric furnace: Electrochem. Ind., vol. 2,1904, p. 396. 
b Schoel, G. P., loc cit. 






166 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

In almost all plants the purest raw materials available are obtained 
for making ferrosilicon. As already mentioned, the introduction of 
slag-forming materials into the charge is thus prevented, and the 
presence of objectionable impurities such as phosphorus and sulphur 
in the product is avoided. With raw materials containing bases 
the silica intended for the product combines with the bases to form 
slag with such a high percentage of silica as to be very sticky, so that 
the pieces can be removed from the furnace only by fishing them 
out as they work to the surface around the electrode, although some 
of the slag may be tapped with the ferrosilicon. Owing to the 
strongly reducing nature of the process most of the phosphorus and 
sulphur charged goes into the metal. The sulphur, however, is 
slagged to a small extent. 

CHARACTER OF FERROSILICON PLANTS. 


Ferrosilicon plants are arranged and use the same general types 
of furnaces as have already been described. The Meraker, Ugine, 
and Livet works may be considered as typical. Conrad and Pick a 
have made a design of a works using 2,000 kilowatts, as shown in 
figures 55 and 56. There are two three-phase furnaces, each of 
2,000 kilowatts capacity. Only one is operated at a time, the others 
being held in reserve. Each furnace has its own three transformers 
connected each to a phase in delta connection. The quartz is hauled 
up an incline to a crusher above, from which it falls into bins below. 
From the bins it is drawn into a car mixed with turnings and coal 
and raised on an elevator to the charging floor of the furnace. The 
general arrangement of the works is similar to that of other works. 
The total space occupied by the plant is 162,000 square feet distrib¬ 
uted as follows: 


Electric furnaces. 

Transformers. 

Packing room. 

Setting up of electrodes 
Crushing and mixing... 

Repair room. 

Coal room. 

Turnings store. 

Quartz store. 

Finished product room. 

Tool room. 

Office, laboratory. 

Yard, tracks. 


Square feet. 
. 12,950 

. 6,470 

. 4,850 

. 3,240 

. 6,470 

. 2,580 

. 12,950 

. 3,240 

. 32,400 

. 6,470 

. 3,240 

. 4,850 

. 64,800 


162,000 


a Conrad, W., and Pick, W., Die Herstellung von Hochprozentigen Ferrosilizium im elektrischen Ofen, 
1909. Rev. de Metallurgie, vol. 9,1912, p. 362. 

















EERROSILICON. 


167 


PRACTICE. 

METHOD OP CHARGING. 

The raw materials are all thoroughly mixed before being charged 
into a ferrosilicon furnace. Charging may be from the tapping floor 
by a man shoveling the charge into the top of the furnace, or charg- 



. a. 


ing may be from a floor at the furnace top, the usual arrangement 
in modern works. In charging the material is placed at intervals 
around the electrodes, so that the top of the furnace never contains 
molten material except when some works up around the electrode. 
The electrode projects about 1 foot into the charge, and around the 
44713°—Bull. 77—16-12 










































































































































































168 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

end the material is molten and maintains a space of a fraction of an 
inch, so that the arc is maintained in the gas formed in the space. 
The arc is called a freeburning arc. By this method there is a lower 
power consumption than if the furnace is operated as a resistance 
furnace entirely. It is essential that the top of the furnace be 
covered with unmelted material, so as to cause less electrode and raw- 
material consumption. By operation with a covered bed of fusion, 
the silicon which is volatilized at a temperature higher than 2,000° 
C. is condensed in the upper part of the furnace. The unmelted 
charge also causes the coal consumption to be lower. In producing 




50 per cent ferrosilicon in a furnace operated with an uncovered bed 
there were losses of 53.7 per cent of the quartz charged and 43.5 per 
cent coal by volatilization and oxidation,® as compared with 13.01 
per cent quartz and 27.58 per cent coal in a modern furnace working 
with a cold top. As a result of this decrease of losses the efficiency is 
much increased. In the furnace operating with an uncovered bed and 
making 50 per cent alloy the power consumption was 7.25 kilowatt- 
hours per pound, or 16,350 kilowatt-hours per long ton. In operation 
with a covered bed the energy used was 3.16 kilowatt-hours per pound, 


a Conrad, W., and Pick, W., Die Herstellung von Hochprozentigen Ferrosilizium im elektrischen Ofen, 
1909. Rev. de M^tallurgie, vol. 9, 1912, p. 362. 











































































































































FERROSILICON. 


169 


or 7,100 kilowatt-hours per long ton. With the furnace having an 
uncovered bed the efficiency was 25 per cent, and with the furnace 
having a covered bed the efficiency was 57.28 per cent. The low 
efficiency of the furnace with an uncovered bed was not due entirely 
to the system of operation, but was also due to the fact that the 
furnace was of 200 kilowatts capacity, as compared with a capacity 
of 1,500 kilowatts for the furnace with the covered bed. These 
examples also show the great strides made in the improvement of 
furnaces and of operating efficiency in the 10 years from 1900 to 1910, 
as the small furnace was one of the first to be built and the larger 
one of modern design. 

TAPPING. 

The furnace is tapped as seldom as possible. The necessity of 
tapping is indicated by the irregularity of the current as shown by 
the meters and the irregular blowing of gas out of the furnace, also, 
when the metal has been too close to the electrode there is an inter¬ 
mittent pounding sound. The shortest interval is about two hours. 
The length of the intervals depends upon the percentage of silicon 
in the product and the size of the furnace. In tapping, an iron rod 
is driven into the tap hole. If material with a high percentage of 
silicon is being made, it is sometimes necessary to attach the rod to 
the circuit and burn out the hole with an arc. The tap hole is 
plugged with fine clay or some similar refractory material. 

A furnace operating steadily in making ferrosilicon has white fumes 
of silicon passing off at the top with carbon monoxide burning to 
dioxide around the electrodes. In some laboratory experiments by 
the writer, the condensed fumes from a ferrosilicon furnace contained 
67.69 per cent Si0 2 , 9.72 per cent A1 2 0 3 , 4.11 per cent FeO, 0.20 per 
cent MgO, and 1.90 per cent CaO, the rest probably being carbon. 

CHANGING ELECTRODES. 

When it is necessary to shut off the current in changing an electrode, 
if the shutdown be a long one, bars of iron are stuck down through 
the charge to make contact with the bottom or between the electrodes, 
so as to avoid difficulty in starting up. The molten charge is a good 
conductor, but is not so when solid. 

Electrodes are replaced by simply swinging one in over the furnace 
to replace the holder and the burnt electrode removed. If the elec¬ 
trode has a tendency to rise in the furnace when a fixed voltage is 
being maintained by hand regulation of the electrode, quartz, a 
relatively poor conductor, is charged around the electrode, so that it 
becomes necessary to lower the electrode to maintain the current 
steadily. If the reverse is the case, coal is added to put in a good 
conductor for raising it. 


170 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

SLAG FORMATION. 

Because of the use of pure raw materials, comparatively little slag 
is formed in a ferrosilicon furnace. The slag formed consists of sili¬ 
cates of aluminum and lime or magnesia. They are very high in silica 
and rather infusible. The addition of more basic materials to make 
them fusible would do no good, because it would simply draw more 
silica from the charge and increase the total slag. As the percentage 
of silicon in the product increases, the specific gravity of the product 
decreases, so that it is difficult to obtain separation of slag and metal 
if the slag is sticky. In the manufacture of the 25 per cent alloy, slag 
is permissible, with a silicon content of 50 per cent, operation is dif¬ 
ficult and with higher percentages is impossible if slag is present. 
As a rule, these slags are so thick that they are not tapped but boil 
up around the electrode and are removed there. The results of some 
analyses® are as follows: 

Per cent. Per cent. Per cent. 


Si0 2 . 68.86 67.60 79.25 

A1 2 0 3 . 13.80 19.63 9.04 

CaO. 26.40 17.00 19.17 

Fe 2 0 3 . 1.96 1.02 3.50 


The ferrosilicon is tapped into cars lined with sand or carbon. It 
is dumped to cool and broken into small pieces with hammers and 
weights. In tapping, iron must be kept away from the molten ferro¬ 
silicon as in the molten condition it dissolves iron readily. The 
product is usually packed in 100-kg. (220-pound) iron drums or in 
kegs. 

RESULTS OF EARLY OPERATIONS. 

In the early operations there was much excess raw material charged 
for the amount of product produced. In a small 200-kw. furnace of 
the old design, the following charges were made: 6 Twenty-five per 
cent product—40 parts quartz, 40 parts iron, 20 parts of anthracite; 
50 per cent product—58 parts quartz, 13 parts iron, 29 parts anthra¬ 
cite; 70 per cent product—66 parts quartz, and 34 parts anthracite. 
The coal contained 20.71 per cent ash (2 to 3 per cent Si0 2 ), 71.29 
per cent carbon, 1.08 per cent hydrogen, 1.11 per cent water, and 0.48 
per cent sulphur. The turnings had 98 per cent iron. The quartz 
was 98.5 per cent Si0 2 , and 0.5 per cent Fe 2 0 3 . For a 50 per cent 
ferrosilicon the following charge was used in an 1,800-kw. modern 
furnace and may be considered as representative practice: Fifty- 
four parts of quartz, 20 parts of iron turnings, 30 parts of charcoal. 
The quartz contained 95 per cent Si0 2 and 3.9 per cent Fe 2 0 3 ; the turn¬ 
ings, 98.5 per cent iron; and the charcoal, 71.9 per cent carbon and 
4 per cent ash. 


«Conrad, W., and Pick, W., Die Herstellung von Hochprozentigen Ferrosilizium in elektrischen Ofen, 
1909. Rev. de Metallurgie, vol. 9,1912, p. 362. 
b Conrad, W., and Pick, W., Loc. cit. 









EERROSILICOX. 


171 


POWER CONSUMPTION. 

The power consumption with this charge was 7,100 kilowatt-hours 
per long ton of 50 per cent ferrosilicon. Of the total energy 57.28 
per cent was usefully used, 8.61 per cent was used in volatilizing sili¬ 
con, and 0.23 per cent in volatilizing iron, and 33.88 per cent was 
lost by induction, radiation, and other losses. The electrode con¬ 
sumption during a month of steady operation averaged 84 pounds 
per long ton of 50 per cent product. Amorphous-carbon electrodes 
were used. 

When iron turnings are used, the power consumption of a modern 
furnace of 750 kilowatts or more capacity is 6,800 to 8,000 ldlowatt- 
hours per ton of 50 per cent ferrosilicon, and about 3,500 to 4,000 
kilowatt-hours for the 25 to 30 per cent grade. As has already been 
noted in the discussion of the theory of power consumption, the 
power consumption is considerably higher if iron ore is used instead 
of turnings. With the ore mentioned on page 165, one company made 
28 per cent ferrosilicon with a power consumption of 5,930 kilowatt- 
hours per ton.° 

Louis 6 estimates the power consumption in the production of 
various grades of ferrosilicon, as shown in the table below, the fig¬ 
ures being based on a 7,500-kw. plant and 750-kw. units: 


Power consumption in ferrosilicon manufacture. 


Raw materials. 


Quartzite, coke, iron turnings. 

Do. 

Do. 

Slag and coke. 

Slag, charcoal, sand. 

Do. 

Do. . 

Quartz, iron ore, coke, or anthracite 

Do. 

Enrichment of 25 per cent. 


Silicon in 
product. 

Power 
consump¬ 
tion per 
pound. 

Power consumption. 

Per cent. 

Kilowatt- 

hours. 

Kilowatt- 

hours. 

Kilowatt- 

years. 

25 

1.82 

4,080 

0.46 

50 

3.64 

8,160 

.92 

75 

5.46 

12,240 

1.38 

25 

1.82 

4,080 

.46 

30 

2.18 

4,890 

.56 

35 

2.54 

5,600 
8,160 

.64 

50 

3.64 

.92 

25 

2.18 

4,890 

.56 

50 

4. 36 

9,780 

1.12 

50 

4.36 

9,780 

1.12 


WORKMEN REQUIRED. 

A small furnace of 200 to 300 kw. requires one man for charging. 
Two men for six furnaces can perform the remaining duties, such as 
tapping and mixing charges, the total number necessary for six 
furnaces, being eight men. A large furnace of 2,000 to 3,000 kw. can 
be entirely operated by five men. 

a Schoel, G. P., Manufacture of ferro-alloys in the electric furnace: Electrcchem. Ind., vol. 2,1904, p. 396. 
b Louis, J., La fabrication des ferrosilicium au four electrique: Jour, du Four Electrique et de Lumiere,. 
Oct. 1,1910, p. 415. 





















172 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

PRODUCTS. 

Electric-furnace ferrosilicon is produced in four grades, classified 
according to silicon content, which is as follows for each grade: 

Twenty-five to thirty per cent, 45 to 50 per cent, 75 to 80 per cent, and 
90 to 95 per cent. The selling of these products is based entirely 
upon the silicon content, because the carbon content, owing to its 
usual low percentage, has no effect upon the price, as in other alloys. 
The current prices for the various grades are given in the table on 
page 140. Below are given the results of analyses of the four grades 
of electric-furnace ferrosilicon: 

Results of analyses of four grades of ferrosilicon. a 


Silicon content. 


Constituent. 

25 to 30 
per cent. 

45 to 50 
per cent. 

75 to 80 
per cent. 

90 to 95 
per cent. 

Silicon. 

30.50 

49.50 

78.00 

88.50 

Iron. 

68.00 

49.00 

20.00 

9.30 

Manganese. 

.35 

.30 

.25 

.15 

Aluminum. 

.10 

.15 

.10 

.15 

Magnesium. 

.10 

.15 

.30 

.30 

Carbon. 

.35 

.30 

.30 

.25 

Sulphur. 

.02 

.015 

.015 

.015 

Phosphorus. 

.04 

.03 

.03 

.03 



a Girod, P., Studies on the electrometallurgy of ferro-alloys and steels: Trans. Faraday Soc., vol. 6, 
1911, p.172. 


In spite of the agitation against the manufacture of ferrosilicon 
containing between 38 and 65 per cent silicon because of the poisonous 
gases that are claimed to be given off, this grade is the one most 
largely made. Moreover, many persons believe that the gases can be 
eliminated if the ferrosilicon is made from pure materials. 

PACKING AND TRANSPORTATION OF FERROSILICON. 

Details on the packing of ferrosilicon in Sweden have recently been 
obtained by the Department of Labor. a The Gullspangs Elektro- 
kemiska Aktiebalag use iron-bound wooden cases in two sizes, one 
for the 50 per cent # product containing 130 kilograms (287 pounds), 
and one for the 75 per cent product containing 160 kilograms (353 
pounds). The cases are unlined but are made of rabbeted boards. 
Recently the practice of packing the ferrosilicon in sheet-metal cylin 
ders or drums containing 170 kilograms (375 pounds) was begun. 
The drums have four holes of about i-inch diameter in the top to 
prevent excessive gas pressure. 

The Aktiebolaget Heroults Elektriska Stal until recently packed 
ferrosilicon in old wooden oil barrels. Now the company has adopted 


a Anon., Packing and transport of ferrosilicon in Sweden: Met. and Chem. Eng., vol. 11,1913, p. 87. 





















FERROSILICON. 173 

sheet-iron barrels with wooden heads. The barrels hold 300 kilo¬ 
grams (660 pounds). 

The regulations for transportation differ widely. In Germany 
water-tight packing is required. As a result, ferrosilicon is packed in 
barrels that are both water and gas tight. Some English railroads 
require that each package must have three 1-inch holes to permit 
the escape of gases. For safe transportation uniform regulations 
should be enforced by all countries. 


COST OF MANUFACTURE. 

The cost of manufacture of ferrosilicon depends more upon the 
price of electric power than upon any other item. This is because 
of the large amount of power necessary and the low cost of the raw 
materials composing the charge. Consequently a large part of the 
electric-furnace ferrosilicon used in the United States is imported 
from Europe and Canada. Of plants engaged in the manufacture of 
ferrosilicon the writer found none in which the power cost was over 
$20 per kilowatt-year and the average was about $13 per kilowatt- 
year. 

An estimate of the cost of production of 50 per cent ferrosilicon 
is given in the table below. The calculations are on the basis of two 
2,000-kilowatt furnaces, one operating and the other kept in reserve. 
The Norwegian plant is within 60 miles, the French plant within 200 
miles, and the American works assumed to be within 100 miles of sea¬ 
board. Labor conditions are considered to be as found in the various 
countries. 


Cost of 'production of 50 per cent ferrosilicon per ton {2,240 pounds). 


« 


Item. 


1,170 pounds of iron. 

2,750 pounds of quartz. 

1,470 pounds of coal. 

50 pounds of electrodes. 

0.8 kilowatt-year. 

Labor, salaries. 

Repairs and maintenance. 

Amortization and depreciation 5 per cent 

each. 

Interest on $50,000 at 6 per cent. 

General and packing. 

Total. 


vay. 

France. 

United States. 

Total 

Cost of 

Total 

Cost of 

Total 

cost. 

unit. 

cost. 

unit. 

cost. 

$7.30 

$14.00 

$7.30 

$8.00 

$4.17 

2. 46 

2.00 

2. 46 

2. 00 

2. 46 

5.30 

6.00 

3.95 

5.00 

3.30 

2.00 

.03 

1.50 

.04 

2.00 

6. 62 

18.66 

15.00 

26.66 

21.30 

10.00 

a. 80 

8.00 

ol.50 

15.00 

5.00 


5.00 


5.00 

2.00 


2.00 


2.00 

1.20 


1.20 


1.20 

4.00 


4.00 


4.00 






45.88 


50.41 


60. 43 







Cost of 
unit. 


$14.00 
2.00 
8.00 
.04 
8.30 
ol 


a Minimum for eight hours. 


The electrode consumption is based upon the use of electrodes 
threaded for continuous feeding, a practice not now universally fol¬ 
lowed in ferro-alloy plants. The figures indicate that it costs $14.55 









































174 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

or 31.7 per cent more to manufacture 50 per cent ferrosilicon in the 
United States than in Norway. This difference may be considered 
as due largely to the price of power. The difference in the total cost 
of power in Norway and the United States for a ton of 50 per cent 
ferrosilicon is $14.68 per ton. Labor is also lower, but this is offset by 
the higher cost of raw materials abroad. The duty on ferrosilicon 
under the Underwood bill is 15 per cent ad valorem. The selling 
price of 50 per cent ferrosilicon f. o. b. Pittsburgh, Pa., is $70 to $75 
per long ton. 

USES. 

The chief use for ferrosilicon is for the deoxidation of steel by the 
formation of silica or silicates with any free oxygen or oxides, the 
silica or silicates thus formed passing into the slag. A considerable 
amount is used for making fixed additions to steel. The grade 
containing 25 to 30 per cent silicon is used as a substitute for blast¬ 
furnace grades containing 10 to 12 per cent silicon. It is especially 
useful for direct addition to the open-hearth furnace, the cupola, or 
the converter, but may be added in the ladle. It is compact, in 
large pieces, and of sufficient specific gravity to sink readily in the 
bath. It reacts more energetically than does the alloy with the 
lower percentage of silicon and the quantities employed need not be 
so large. This grade is used chiefly for fixed additions of silicon. 

Ferrosilicon that has 45 to 50 per cent silicon is particularly 
employed for deoxidation. It reacts like the 25 to 30 per cent alloy 
but more energetically, and is used when the greater specific gravity 
of the latter is not essential. It has a lower fusion point than the 
lower grade. It is subject to disintegration and is the only grade 
from which poisonous gases have been known to emanate. It is used 
in greater quantity than any of the other grades. 

The grade containing 75 per cent silicon is employed for additions 
to ordinary castings. It can be used to modify a casting so as to 
obtain either a white or a gray casting by addition to the casting 
ladle. For a fixed addition in the production of silicon steels, such as 
transformer steel, 75 to 90 per cent ferrosilicon is employed. 

Hadfield . a developed silicon steel containing 1 to 5 per cent silicon, 
but the usual grade contains 2.75 per cent silicon with the smallest 
possible amounts of carbon, manganese, and other impurities. After 
a double-heating treatment this steel has a higher magnetic permea¬ 
bility than the purest iron, but also, as is characteristic of silicon 
steels, has a high electrical resistance. As a result of its high per¬ 
meability, it has a low hysteresis loss, and is the most desirable 
material known for use in electrical generating machinery. 


a Stoughton, B., The metallurgy of iron and steel, 1912, p. 406. 




FERROTITANIUM. 175 

ALLOYS OF IRON AND SILICON WITH OTHER ELEMENTS. 

For the use of foundries several alloys have been manufactured, 
such as ferrosilicomanganese-aluminum, ferrosilico-aluminum, and 
silicocalcium-aluminum. These alloys are intended for use as rapid 
deoxidizing and refining agents, and form easily fusible silicate slags 
of the other elements, which rise to the surface of the bath, as they are 
of low specific gravity. These alloys are too expensive for use in the 
large-scale production of ordinary steel. 

Ferrosilicomanganese-aluminum is made in two grades, one con¬ 
taining 18 to 20 per cent silicon, 18 to 22 per cent manganese, and 9 to 
12 per cent aluminum; and the other containing 9 to 11 per cent 
silicon, 9 to 11 per cent manganese, and 4.5 to 6 per cent aluminum, 
the rest in both grades being iron and carbon. The alloy is made by 
melting ferrosilicon-manganese and aluminum together. It is added 
in the ladle or molds, or in the furnace itself. It is used largely for 
cast steel, when the steel is cast directly into molds. 

Another similar alloy is ferrosilico-aluminum, containing about 45 
per cent silicon and 12 to 15 per cent aluminum, the rest being iron 
and carbon. It is made by alloying ferrosilicon and aluminum in the 
electric furnace. This alloy is intended for deoxidizing purposes. 
It is added in the electric steel furnace just after removal of the oxidiz¬ 
ing slag. The alloy is in powder form and is also used in the tapping 
ladle for removing oxides. Sometimes it is added to the ingot molds. 
The electric furnace is the only furnace to which it is added for the 
manufacture of steel, because in the open hearth or converter there 
is great loss of the alloy. Ferrosilico-aluminum has not the reducing 
power of aluminum, but it is sufficient for the removal of most oxides. 

Ferrosilicocalcium-aluminum is an electric-furnace product con¬ 
taining 50 to 55 per cent silicon, 18 to 22 percent calcium, 12 to 15 
per cent iron, 4 to 5 per cent aluminum, 1 to 1.25 per cent carbon, 0.35 
per cent magnesium, 0.22 per cent manganese, 0.075 per cent sulphur 
and 0.03 per cent phosphorus. It is a strong deoxidizer and desul- 
phurizer, and gives highly fluid slags. It is added in the electric 
furnace after the removal of the oxidizing slag. It can be added in 
the casting ladles, crucibles, or molds. Because of its high cost, its 
use is restricted to the manufacture of high-class steels. 

FERROTITANIUM. 

Ferrotitanium has been developed for use in steel manufacture since 
the introduction of the electric furnace for ferro-alloy production in 
1900. In 1892 Rossi obtained a patent on the reduction of titan- 
iferous ores in the blast furnace. Later he attempted to make a 
ferrotitanium in the blast furnace and crucible but could not obtain 
a product with a high percentage of titanium. Subsequent experi- 


176 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

mental work in the electric furnace resulted in the commercial estab¬ 
lishment of the manufacture of ferrotitanium for steel making. For¬ 
eign manufacturers of ferro-alloys produced ferrotitanium on a small 
scale in the electric furnace. A considerable amount is made by the 
Goldschmidt thermit process. This grade is carbon free but contains 
as high as 5 per cent of aluminum, and is more expensive than the 
electric-furnace product. 

All ferrotitanium now produced is manufactured either by reduction 
of ores with carbon in the electric furnace or by the Goldschmidt 
thermit process, most of it being made in the electric furnace. No 
other process gives a high enough temperature, 2,000° C., or over, 
for reduction of titanium from the oxide. In Rossks first patent a 
on ferrotitanium, he specifies the reduction of titaniferous ores and 
rutile with carbon in an electric-resistance furnace to produce an alloy 
containing more than 5 per cent titanium and some carbon. The 
reduction is performed over a bath of molten iron. Another patent, 6 
granted the same date, covers the use of titaniferous slag in the same 
manner. In 1900 he procured a patent 0 on the reduction of titanium 
ores by the addition of ores to a bath of molten reducing metal, such 
as aluminum, in the electric furnace. In 1901 Rossi d was granted 
a patent on a process for the concentration of titanium in slag by 
reducing the iron and silicon of a titaniferous ore with carbon at a 
temperature lower than the reducing point of titanium oxide. 

Ferrotitanium is manufactured commercially at one plant in a 
Siemen’s type of electric furnace of about 500 kw. capacity. A 
molten bath of iron from scrap iron or steel is first formed in the bot¬ 
tom of the furnace. Titaniferous ore, titaniferous slag, or rutile, is 
then mixed with carbon in the proper proportion, charged on the 
molten bath, and reduced in the arc. The product is tapped off and 
broken up for packing. If the slag is high in titanium it is run back 
through the furnace. The titaniferous ore contains 34.36 per cent 
Ti0 2 , 50.53 per cent FeO, 4.14 per cent Si0 2 , and 2.20 per cent Al 2 O s . 
The product obtained from this reduction without any refining con¬ 
tains 10 to 15 per cent titanium, 5 to 8 per cent carbon, and 0.35 to 
1 per cent silicon. By refining this alloy, with rutile as a decarbur- 
izer, an alloy is made that has 10 to 15 per cent titanium, less than 
1.0 per cent carbon, and 0.35 to 1 per cent silicon. In a later patent^ 
in order to reduce the volatization loss of titanium, Rossi specifies 
the charging of lime on the molten iron bath, followed by a charge 
of titanic acid, lime, and carbon, when reduction takes place accord¬ 
ing to the following reaction: 

Ca0+Ti0 2 +5C=CaC 2 +Ti+3C0 


« U. S. patent No. 609466, August 23,1898. 
& U. S. patent No. 609467, August 23, 1898. 
cU. S. patent No. 648439, May 1,1900. 


dU. S. patent No. 668266, February 19,1901. 
e U. S. patent No. 1019528, March 5,1912. 




THE PRODUCTION OF FERROTUNGSTEN. 177 

The titanium sinks through the lime slag to the iron, and the reduc¬ 
ing cover of calcium carbide protects the bath from oxidation. Be¬ 
cause of its cost rutile (Ti0 2 ) is not so extensively used in the man¬ 
ufacture of ferrotitanium as a titaniferous ore. Rutile sells for $100 
to $150 per short ton. 

The presence of carbides in electric-furnace ferrotitanium have 
been claimed to prevent its ready solution in steel, so that it would 
not do the work of carbon-free ferrotitanium. However, there does 
not appear to be over 0.25 per cent of combined carbon in the alloy 
containing 9 per cent carbon. The remaining carbon is present as 
graphite and on addition of the ferrotitanium to the steel bath part 
of the carbon combines with the steel to form carbides and the rest 
rises to the surface and is lost in the slag. 

Ferrotitanium is added to steel and cast-iron baths for the purpose 
of final deoxidation of the metal and its impurities, following the 
usual treatment for this object by means of manganese and silicon.® 
Titanium has a strong affinity for oxygen and also seems to cause 
occluded or oxidized substances in the steel bath to separate readily. 
The resulting iron or steel is tougher and stronger after treatment. 
The alloy is added in the ladle into which the product of either the 
open-hearth furnace or the converter is being poured. It should be 
added last after carburizing and other alloys have been used, or 
much will be wasted. Too much slag should not be present, as tita¬ 
nium acts energetically with the slag. Ferrotitanium should never 
be preheated before being added or used in conjunction with alumi¬ 
num. Little ferrotitanium is used for fixed addition to steel. 

ELECTRIC SMELTING OF TUNGSTEN ORES AND THE 
PRODUCTION OF FERROTUNGSTEN. 

* 

HISTORY. 

Ferrotungsten with a low percentage of tungsten was made by 
Berthier in 1834. Caron studied iron tungsten alloys in 1868 and 
determined that the hardness increased the percentage of tungsten. 
In 1866 Biermann made some ferrotungsten from tungsten trioxide 
and iron in the crucible. This method was used up to the introduc¬ 
tion of the electric furnace in 1900, since which time most of the ferro¬ 
tungsten has been made in the electric furnace, although small 
quantities, containing less than 60 per cent tungsten, are still manu¬ 
factured in the crucible. The crucible product is made by the 
reduction of tungsten trioxide with carbon. In electric-furnace 
methods raw ores or concentrates are reduced. 


a Stoughton, B., The metallurgy of iron and steel, 1908, p. 169. 




178 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


EXPERIMENTS OF STASSANO. 

Stassano a conducted experiments on the manufacture of ferro¬ 
tungsten from wolframite concentrates in a 75-kw. electric furnace, 
with charcoal as a reducing agent. The concentrates, charcoal, and 
lime were crushed and briquetted with a 25 per cent solution of 
sodium silicate as a binder. Theoretically the ferrotungsten should 
have contained 71.5 per cent tungsten, 20.6 per cent iron, 7.1 per 
cent manganese, and 1 per cent silicon. The results of Stassano s 
experiments are tabulated below: 


Constituent of ore charged: Percent. 

W0 3 . 69.8 

Si0 2 . 2.0 

FeO.... 20.5 

MnO. 7.3 

S.2 

p. Trace. 

Constituent of charge: Parts. 

Wolframite. 1,000 

Charcoal. 190 

Lime. 40 

Mn 2 Si0 3 . 80 


Composition of products of three experiments. 


Constituent. 

Proportion in experiment No. — 

1 

2 

3 

W. 

Per cent. 
58.00 

Per cent. 
65.66 

Per cent. 

69. 76 

C. 

2. 40 

2.062 

2.50 

Mn. 

3.192 

3.50 

3.60 

Si. 

1.244 

1.02 

1 . 3 a 

P. 

Trace. 

Trace. 

Trace. 

S. 

Trace. 

Trace. 

Trace. 

Kilowatt-hours per pound of product. 

2.73 

2.95 

3.9a 

Kilowatt-years per ton (2,000 pounds) of product. 

.62 

.67 

.78 


The average energy consumption was 3 kilowatt-hours per pound, 
or 0.68 kilowatt-year per ton. These experiments showed the possi¬ 
bility of reducing wolframite with carbon in the electric furnace, but 
did not show where the loss in tungsten occurred. It is not apparent 
whether the low tungsten content was the result of slag losses or the 
presence in the furnace of some unnoted iron which diluted the 
alloy. 

EXPERIMENTS WITH COLORADO FERBERITE. 

In 1911 the writer performed some experiments on the reduction 
of ferberite with carbon to produce ferrotungsten in the electric fur- 


a Stassano, E., Treatment of iron and steel in the electric furnace. Electrochem. and Met. Ind., vol. 6, 
1908, p. 315. 


































THE PRODUCTION OF FERROTUNGSTEN. 


179 


nace.° The furnace was one described herein in the discussion of the 
production of ferrochrome. Analyses of the coke and lime employed 
are given in the table on page 128. Pure calcium fluoride was used. 
The iron ore contained 94.9 per cent Fe 2 0 3 , 4.10 per cent Si0 2 , 0.79 
per cent CaO, 1.46 per cent A1 2 0 3 , 0.05 per cent P, and 0.03 per cent S. 
Ferberite concentrates from Boulder County, Colo,, of the following 
composition were obtained: 58.72 per cent W0 3 (46.6 per cent 
tungsten), 30.08 per cent FeO (23.4 per cent iron), 2.55 per cent MnO 
(0.84 per cent manganese), 4.86 per cent Si0 2 , 3.46 per cent CaO, 0.34 
per cent P, and 0.20 per cent S. 

In each experiment a decarburizing slag of iron ore, lime, and fluor¬ 
spar was added to the furnace when reduction of the charge had been 
completed and allowed to act for 10 to 20 minutes. It was tapped 
from the furnace with the ferrotungsten and the slag from reduction. 

As shown in the table following, the alloys obtained, with two 
exceptions, were somewhat lower in tungsten than had been calcu¬ 
lated. This was the result of three causes: First, the presence in the 
furnace of iron due to hanging of a previous run with Iron ore; sec¬ 
ond, the loss of tungsten in the slag; and, third, the iron reduced from 
the decarburizing slag. The carbon content of all of the alloys was 
low for ferrotungsten, a condition clearly assisted considerably by 
the use of the decarburizing slag of iron oxide and lime. It was 
manifest that with a longer decarburization period the carbon in the 
alloy could have been reduced still further. The greater part of the 
manganese in the charge was either slagged or volatilized. The per¬ 
centage of silicon was high in some of the products, but much lower 
when there was no iron ore in the charge. Phosphorus and sulphur 
were easily slagged in spite of a high percentage of both in the ore. 
The slags contained 4.66 to 8.64 per cent tungsten oxide (or 3.7 to 
6.8 per cent tungsten), and ferrous oxide in about the same per¬ 
centage. 

The commercial ferrotungsten from the electric furnace contains 
50 to 80 per cent tungsten and 0.5 to 4 per cent carbon. 

During the experiments 32 pounds of ferrotungsten was made, or 
an extraction of 83.8 per cent. The electrode consumption for the 
two experiments in which it was determined averaged 150 pounds per 
ton. This figure would be considerably reduced in large-scale opera¬ 
tions. The average energy consumption for the seven experiments 
was 3.46 kilowatt-horns per pound tapped, or 0.79 kilowatt-year per 
ton. The ferrotungsten was hard and brittle, and castings made 
from it were free from blowholes. « 

a Keeney, R. M., The production of steels and ferro-alloys directly from ore in the electric furnace: Iron 
and Steel Inst., Carnegie Scholarship Memoirs, vol. 4,1912, p. 108. 





180 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 
Detailed results of the experiments are tabulated below: 


Results of experiments on the production of ferrotungsten directly from ore. 


Experiment No. 

1 

2 

3 

4 

5 

6 

7 

Charge: 








Ferberite.pounds.. 

Hematite.do_ 

5.00 
1.50 

10.00 
3.00 

5.00 

1.50 

5.00 

1.50 

6.00 

6.00 

6.00 

Coke.do_ 

1.25 

3.00 

1.37 

1.52 

1.12 

1.12 

1.12 

Lime.do_ 

.75 

1.56 

.90 

.95 

.75 

.75 

.75 

Fluorspar.do_ 

.062 

1.24 

.062 

.062 

.062 

.062 

. 062 

Refining slag: 








Hematite.do_ 

.75 

.75 

.75 

.75 

.75 

.75 

.75 

Lime.do_ 

.20 

.20 

.20 

• .20 

.20 

.20 

.20 

Fluorspar.do_ 

.044 

.044 

.044 

.044 

.044 

.044 

.044 

Composition of alloy: 








Tungsten.per cent.. 

38. 74 

49.64 

41.39 

43.35 

42.19 

37.50 

59.01 

Carbon.do_ 

1.77 

1.82 

2.05 

2.51 

1.66 

2.04 

2.02 

Manganese.do_ 

.32 

.16 

.42 

.38 

.16 

.33 

.16 

Silicon.do_ 

,47 

.31 

.24 

.44 

.14 

.07 

.09 

Phosphorus.do_ 

.044 

.046 

.042 

.048 

.051 

.054 

. 020 ' 

Sulphur.do_ 

.032 

.068 

. 0S9 

.017 

.014 

.021 

.015 

Composition of slag: 








W0 3 .do.... 

8 . 64 

4.14 

7. 20 

4.24 

4.00 

5.28 

4.88 

SiCL.do_ 

30.12 

31.10 

31.00 

31.40 

30.40 

29.28 

29.64 

CaO.do_ 

21.30 

37.00 

30. 00 

24.60 

28. 00 

21.10 

29. 30 

MgO.do_ 

16. 60 

12.00 

19. 60 

26.64 

24.48 

23.64 

18.80 

FeO.do_ 

12.60 

12 . 00 

5.84 

4.52 

5.84 

5.10 

6 . 87 

AI 2 O 3 .do_ 

12.10 

5.70 

5. 24 

6.95 

6.22 

11.67 

7.88 

Wolfram in product, calculated 








percentage. 

Carbon per pound W and Fe, 

50.00 

50.00 

50.00 

50.00 

65.00 

65.00 

65.00 

pounds. 

.202 

.222 

.222 

.212 

.214 

.214 

.214 

Alloy calculated, pounds. 

5.08 

10.16 

5.08 

5.08 

4.30 

4.30 

4.30 

Alloy tapped, pounds. 

2.00 

8 . 78 

5.62 

2 . 20 

6.50 

2.20 

4.62 

Power consumption per pound 








tapped, kilowatt-hours. 

4.76 

2.63 

2.00 

5.78 

1.86 

5.25 

1.96 

Power consumption per ton 








tapped, kilowatt-years. 

1.09 

.60 

.46 

1.32 

.42 

1.20 

.45 


CONCLUSIONS. 

Conclusions drawn from the experiments are as follows: First,, 
ferrotungsten can be produced directly from ferberite in the electric 
furnace; second, by the use of a decarburizing slag before tapping 
the percentage of carbon in the alloy can be kept below 2 per cent; 
third, manganese, silicon, phosphorus, and sulphur do not enter the 
ferro-alloy in high percentages; fourth, the loss of tungsten in the 
slag need not be excessive; and fifth, the power consumption need 
not exceed 3.46 kilowatt-hours per pound of ferrotungsten tapped, 
or 0.79 kilowatt-year per ton. 

THEORY OF TUNGSTEN ALLOYS. 

Several carbides and alloys of iron and tungsten have been isolated 
from ferrotungsten. Moissan ° obtained W 2 C by fusing carbon and 
tungsten in the electric furnace; in the same manner Williams 3 
found WC. Williams obtained 2Fe 3 C.3W 2 C by the reduction of 
tungsten trioxide with carbon in the electric furnace. Behrem 
found Fe 2 W in ferrotungsten containing 50 per cent tungsten. 
Carnot and Goutal isolated Fe 3 W. Benneville isolated Fe 4 W. 


a Guillet, L, Etude industriel des alliages metallique, p. 425. 
















































THE PRODUCTION OF FERROTUNGSTEN. 181 

Bierman found Fe 3 W 2 C. The double carbide is not of constant com- 
position. W 2 Si 3 is known to exist, and the compound WSi is believed 
to exist. W 2 Si 3 was obtained by Moissan synthetically in the electric 
furnace. The carbides W 2 C and WC are both iron gray and very 
bard. WC fuses with difficulty. 

REACTIONS. 

Ferro tungsten can be made by reduction of wolframite, ferberite, 
or scbeelite with aluminum, silicon, or carbon. Rossi ° reduced 
ferberite with aluminum in a Siemens type of electric furnace. An 
alloy containing 75.9 per cent tungsten, 21.4 per cent iron, 1.6 per 
cent silicon, 0.08 per cent sulphur, and 0.9 per cent carbon was made 
from concentrates containing 69.8 per cent W0 3 , 20.25 per cent FeO, 
and 5.04 per cent Si0 2 . The reaction used is as follows: 

3Fe 2 W0 4 +8Al=3Fe 2 W+4Al 2 0 3 

For the reduction of 100 parts of 62.3 per cent tungsten ferrotung- 
sten from 122 parts of ferberite 24.2 parts of aluminum is necessary. 

Gin has produced ferrotungsten by the reduction of scheelite with 
a bath of 20 per cent ferrosilicon in the electric furnace according to 
the following reaction: 

3CaW0 4 +4Fe 2 Si=(2Fe 2 W+Fe 3 W)+3CaSi0 3 +FeSi0 3 

v 

The most common method for the production of ferrotungsten is 
by the reduction of ferberite, wolframite, or scheelite concentrates 
in the electric furnace with carbon as a reducing agent, followed by 
a subsequent decarburization and refining. Wolframite or ferberite 
is readily reduced in this manner, but there is difficulty in the reduc¬ 
tion of scheelite. Ferberite is wolframite [(FeMn)WOJ, in which 
the manganese is replaced by iron so as to give (FeFe)W0 4 . Reduc¬ 
tion occurs with carbon according to the following reaction: 

Fe 2 W0 4 +4C=Fe 2 W+4C0 

Theoretically the product contains 62.3 per cent tungsten. For 
the reduction of 100 parts of this alloy from 122 parts of ferberite 
16.2 parts of carbon is necessary. 

Scheelite is now smelted by one company with sulphide of iron 
and carbon in the electric furnace. 6 Lime is also added to flux the 
silica. The following reaction takes place: 

CaWO 4 +FeS+40=FeW+CaS+4CO 

The product is said to be a ferrotungsten containing little carbon. 

After much experimental work on a large scale, it seems that reduc¬ 
tion with carbon followed by decarburization with iron ore or tung- 


a Rossi, A. J., Ferro-alloys: Mineral Industry, 1903, p. 693. 

b Editorial, Electric production of ferrotungsten: Eng. and Min. Jour., January 20, vol. 93,1912, p. 173. 



182 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

sten concentrates is the cheapest and most efficient method of 
making ferrotungsten in the electric furnace. Aluminum is expensive 
and goes into the alloy to a certain extent, as also does silicon. 

Ferrotungsten may be decarburized by covering the fused metal in 
the electric furnace with hammer scale, when the following reaction 
takes place: 

Fe 6 0 7 +7W 2 C=6FeW 2 +W 2 +7C0.a 

The reaction is not strictly quantitative because there is always 
formed some ferrous tungstate. 

It is possible to make ferrotungsten containing 80 per cent tungsten 
and less than 0.5 per cent carbon by the following reaction: 

Fe 6 0 7 +3W 2 C=5FeW+FeW0 4 +3C0 

Ferberite or wolframite may be used instead of hammer scale. 
Slags high in tungsten are run through the reducing furnace again. 
By the above method carbon can not be reduced below 0.3 per cent in 
the alloy. 

Ferrotungsten with less than 80 per cent tungsten can be made by 
adding metallic iron to the bath and decarburizing with iron oxide and 
hammer scale. 

Alloys with as low a carbon content as 0.15 per cent can be made by 
use of the following reaction: 

3TV 2 C T Fe 2 0 3 -f- 2Fe = 3CO -f- (3Fe"W" 2 -}-Fe). 

Decarburizing with iron oxide has a tendency to cause loss of 
tungsten in the slag by the formation of tungstate of iron. This loss 
may be reduced somewhat by making the decarburizing slag rather 
acid when ferrous silicate is formed, according to the following 
reaction: 

W 2 C+Fe 2 0 3 +2Si0 2 =W 2 +2FeSi0 3 +C0. 

PROCESS OF MANUFACTURE. 

Ferrotungsten is manufactured from ores in three ways, as follows: 
First, by direct reduction with carbon in a crucible; second, by 
reduction in an electric furnace by some reducing agent other than 
carbon; and third, by direct reduction with carbon in an electric 
furnace. 

In manufacture by the crucible process concentrates are placed in 
a clay-lined crucible with the proper proportions of reducing agent 
and flux, and heated to a high temperature in a gas-fired furnace. 6 

a Gin, G., Molybdenum and tungsten: Trans. Am. Electrochem. Soc., vol. 13, 1908, p. 48. 

b Pratt, S. R., Manufacture of metallic tungsten and ferrotungsten in the crucible: Eng. and Min. Jour., 
vol. 90,1910, p. 959. 



THE PRODUCTION OF FERROTUNGSTEN. 


183 


There is considerable wear on the crucible in this method. In making 
a 30 per cent tungsten alloy the crucible will last about three heats, but 
in making a 65 to 75 per cent product it lasts only one heat. Alloys 
with higher percentages of tungsten than this are not made in the 
crucible furnace. 

In the electric-furnace process, ferberite, wolframite, hubuerite, 
or scheelite is reduced with carbon in an arc furnace. As with many 
expensive alloys, the process is generally an intermittent one; that is, 
the reduced charge is tapped from the furnace before another charge 
is added, or the charge is allowed to solidify and is chiseled out of the 
furnace. Sometimes a campaign of several days is made. The 
reduced alloy is either decarburized with refining slags in the same 
furnace or melted and refined later in another furnace. The furnaces 
used are similar in design to the ones described for ferrochrome pro¬ 
duction, but a more complete recovery is effected by the use of a 
tilting rather than a stationary furnace. Wolframite, ferberite, and 
scheelite are reduced easily in the electric furnace, most of the 
manganese being volatilized. Scheelite is more difficult to reduce 
and very sticky basic slags result. There is greater loss in its reduc¬ 
tion, so that it does not command as high a price as the other ores, 
selling for about SI per unit less. The product is tapped into molds, 
broken on cooling, and packed into kegs or boxes. 

The largest producers of tungsten ores are Australia, Colorado, 
California, and Argentina. The standard concentrate contains 60 
per cent tungsten trioxide (W0 3 ). The price varies from $5 to $8 
per unit in the 60 per cent grade; that is, if the rate was $5, a 60 per 
cent concentrate would be worth $300 per short ton. The analysis 
of a typical Colorado ore, ferberite, has been given previously in a 
discussion of the author’s experiments. A typical scheelite contains 
69.50 per cent W0 3 , 16.04 per cent CaO, 0.54 per cent FeO, 0.18 per 
cent MnO, 0.14 per cent P 2 0 5 , and 12.46 per cent Si0 2 . 

The results of analyses of typical ferrotungsten produced in the 
electric furnace are given below. 


Results-of analyses of typical ferrotungsten. 



1 

2 




Per cent. 

Per cent. 

Per cent. 


73.0 

78.5 

83.0 


3.5 

1.7 

.6 


19.0 

18.5 

15.5 


.4 

.3 

.4 


3.5 

.4 

.2 


Trace. 

.1 

.151 


.4 

.1 

.10 


.1 

.05 

.05 


.05 

.04 

.04 


.03 

.015 

.015 




—- 


44713°—Bull. 77—16-13 































184 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

USES. 

Tungsten was first added to steel almost entirely in the form of a 
powder, manufactured chemically. The powder has now been 
replaced by ferrotungsten to such an extent that hundreds of tons of 
the latter is produced annually. It is claimed by ferrotungsten 
manufacturers that there is less loss by oxidation and a more uniform 
solution of tungsten in the steel if ferrotungsten is used. The powder 
manufacturers claim that the alloy is not uniform in composition. 
There is such diversity of opinion in this respect that it is difficult to 
state which is the better, but the production of ferrotungsten is 
increasing. 

Ferrotungsten is used for the addition of tungsten in the manu¬ 
facture of self-hardening or high-speed steels. It is added in the 
furnace or in the crucible. 

Most self-hardening steel contains 4 to 12 per cent of tungsten, with 
2 to 4 per cent of manganese and 1.5 to 2.5 per cent of carbon. It is 
hard without being subjected to any heat treatment or any other 
process for making it so. It can not be made soft, or amended by 
any process known at present. All of the self-hardening steels are 
nonmagnetic. They are used for making tools. The cutting speed 
of tools made from self-hardening steel is not much, if any, greater 
than that of tools made from ordinary carbon tool steel, but the former 
take deep cuts and last longer without grinding. The 2 to 4 per cent 
manganese can be replaced by 1 to 2 per cent of chromium. The 12 
per cent molybdenum can be replaced by 4 to 8 per cent molybdenum. 

High-speed steels contain as much as 24 per cent tungsten and 0.40 
to 0.80 per cent carbon. These steels do not lose their temper or 
toughness at a red heat, so that they are adapted for tools to be used 
for high-speed cutting. In the steel for cutting tools the tungsten 
may be replaced by one-half as much molybdenum. In this way 
6 to 15 per cent molybdenum is used. A little vanadium can be 
added with beneficial results. 

For permanent magnets a steel containing 4 to 5 per cent of tung¬ 
sten and 0.5 to 0.7 per cent of carbon, if heated to a red heat and 
quenched in water, will retain its magnetism better than ordinary 
hardened carbon steel. 

ELECTRIC SMELTING OF VANADIUM ORES AND THE 
PRODUCTION OF FERRO VANADIUM. 

Most of the ferrovanadium made is produced by the thermit 
process, by reduction of the oxide V 2 0 5 in a crucible with carbon, or 
by reduction of vanadate of iron with carbon in a crucible. In 
Europe some ferrovanadium is made by the reduction of the oxide, 
sulphide, or vanadate of iron with carbon in the electric furnace. The 
largest source of vanadium is the Peru deposit of patronite, a sulphide 


PRODUCTION OF FERROVANADIUM. 


185 


of vanadium containing about 60 per cent sulphur and 20 per cent 
vanadium. In Colorado and Utah there are large deposits of low- 
grade carnotite, a uranium and vanadium oxide mineral. Another 
ore found there is roscoelite, which contains vanadium oxide, but no 
uranium. The patronite ore is first roasted and then reduced by the 
thermit process; or in the electric furnace it may be directly reduced 
with lime as a desulphurizing agent and carbon as a reducing agent. 
The other ores are treated by chemical or ore-dressing processes to 
obtain the vanadium as oxide or vanadate of iron, and are then re¬ 
duced with carbon in a combustion or electric furnace or by the 
thermit method. With oxides the electric furnace method is similar 
to the production of ferrotungsten with carbon as a reducing agent. 
The sulphide reduction is similar to that of molybdenite with lime and 
carbon. In several patented methods silicon is used as a reducing 
agent in the electric furnace. The process as performed in the elec¬ 
tric furnace has no novel features beyond those stated regarding 
chromium, tungsten, and molybdenum. Decarburization is with oxide 
of iron ore or oxide ore of vanadium. Vanadium is rather difficult to 
reduce, and as a result excess carbon is used which is absorbed up to 
about 6 per cent by the ferrovanadium. The electric furnace prod¬ 
uct is made in 50 per cent and 25 per cent grades, with carbon varying 
from 1 to 4 per cent. Below are the results of analyses of these 
grades: 

Results of analyses of ferrovanadium. 


Constituent. 

Grade 
with 50 
per cent 
vanadium. 

Grade 
with 25 
to 30 
per cent 
vanadium. 

Vanadium. 

55.00 
40.00 
4.00 
.30 
.10 
.30 
.03 
.04 

34.10 

64.10 
1. 42 

.12 

.12 

.12 

.03 

.009 

Iron. 

Carbon. 

Silicon. 

Aluminum. 

Manganese. 

Sulphur. 

Phosphorus. 



Vanadium acts like titanium as a cleanser and deoxidizer of a steel 
bath, and is also used to add as much as about 0.35 per cent vana¬ 
dium to the steel itself. It is used after ferrosilicon and ferromanga¬ 
nese have been added, so as to prevent loss, and causes deoxidation 
beyond the point obtained by these alloys. It melts without much 
difficulty and attacks the oxides present. Incorporated in the steel 
in proportions up to 0.30 per cent it toughens and adds a great tensile 
strength to the steel. 


















GLOSSARY. 


Inasmuch as this bulletin has been prepared for the purpose of 
giving information to those who are not familiar with electrical work, 
the following glossary, taken mainly from Kent’s “ Mechanical Engi¬ 
neer’s Pocket-Book” (eighth edition) has been prepared: 

UNITS USED IN ELECTRICAL CALCULATIONS. 

Ampere. —The unit of current strength, or rate of flow, represented by I. 

Volt. —The unit of electromotive force, electrical pressure, or difference of poten¬ 
tial, represented by E. 

Ohm.- —The unit of resistance, represented by R. 

Coulomb (or ampere-second).—The unit of quantity, Q. 

Ampere-hour. —3,600 coulombs, Q'. 

Joule (volt-coulomb).—The unit of energy or work, W. 

Watt (ampere-volt, or volt-ampere).—The unit of power, P. 

Farad. —The unit of capacity, represented by C. 

Henry .—The unit of inductance, represented by L. 

If letters are used to represent the units, the relations between them may be 
expressed by the following formulas, in which t represents 1 second and T 1 hour: 

1= f, Q=It, Q'=IT, C=|, W=QE, P=IE. 

As these relations contain no coefficient other than unity, the letters may represent 
any quantities given in terms of those units. For example, if E represents the number 
of volts of electromotive force, and R the number of ohms of resistance in a circuit, 
then their ratio, E-t-R, will give the number of amperes of current strength in that 
circuit. 

The above six formulas can be combined by substitution or elimination, so as to 
give the relations between any of the quantities. The most important of these are 
the following: 

e=ff, c=lf, W=IEt=~t=I 2 Rt=Pt 

K Jh K 

E=IR, R= E r P=^=PR=E=9 E , 


RELATIONS OF VARIOUS UNITS. 


1 ampere. 

1 volt-ampere 

1 watt. 


1 joule. 

1 British thermal unit. 

1 kilowatt, or 1,000 watts. 

1 kilowatt-hour. 

1,000 volt-ampere hours. 

1 British Board of Trade unit 

1 horsepower. 

186 


=1 coulomb per second. 

= 1 watt=l volt-coulomb per second. 

0.7373 foot-pound per second. 

=• 0.0009477 heat unit per second (F). 
.1/746 of 1 horsepower. 

0.7373 foot-pound. 

=< Work done by 1 watt in 1 second. 

0.0009477 heat unit. 

=1055.2 joules. 

=1,000/746, or 1.3405 horsepower. 
=1.3405 horsepower-hours. 

=2,645,200 foot-pounds. 

=3412 heat units. 


1746 watts=746 volt-amperes. 
133,000 foot-pounds per minute. 















GLOSSARY. 


187 


The ohm, ampere, and volt are defined in terms of one another as follows: Ohm, the 
resistance of a conductor through which a current of 1 ampere will pass when the elec¬ 
tromotive force is 1 volt. Ampere, the quantity of current that will flow through a 
resistance of 1 ohm when the electromotive force is 1 volt. Volt, the electromotive 
force required to cause a current of 1 ampere to flow through a resistance of 1 ohm. 

Equivalent values of electrical and mechanical units. 


Unit. 

Equivalent value in other units. 

1 kilowatt-hour. 

1,000 watt hours. 

1.34 horsepower-hours. 

2,654,200 foot-pounds. 

3,600,000 joules. 

3,412 heat units. 

367,000 kilogram-meters. 

0.235 pound of carbon oxidized 
with perfect efficiency. 

3.53 pounds of water evaporated 
from and at 212° F. 

22.75 pounds of water raised from 
62° to 212° F. 

1 h o rsepower- 

0.746 kilowatt-hour. 

hour. 

1,980,000 foot-pounds. 

2,545 heat units. 

273,740 kilogram-meters. 

0.175 pound of carbon oxidized 
with perfect efficiency. 

2.64 pounds of water evaporated 
from and at 212° F. 

17 pounds of water raised from 
62° to 212° F. 

1 kilowatt. 

1,000 watts. 

1.34 horsepower. 

2,654,200 foot-pounds per hour. 
44,240 foot-pounds per minute. 
737.3 foot-pounds per second. 

3,412 heat units per hour. 

56.9 heat units per minute. 

0.948 heat unit per second. 

0.2275 pound of carbon oxidized 
per hour. 

3.53 pounds of water evaporated 
per hour from and at 212° F. 

1 horsepower... 

746 watts. 

0.746 kilowatt. 

33.000 foot-pounds per minute. 

550 foot-pounds per second. 

2,545 heat units per hour. 

42.4 heat units per minute. 

0.707 heat unit per second. 

0.175 pound of carbon oxidized 
per hour. 

2.64 pounds of water evaporated 
per hour from and at 212° F. 

1 joule. 

1 watt second. 

0.000000278 kilowatt-hour. 

0.102 kilogram-meter. 

0.0009477 heat unit. 

0.7373 foot-pound. 


Unit. 


Equivalent value in other units. 


1 foot-pound... 


1 watt 


1 watt per 
square inch. 


1 heat unit 


1 heat unit per 
s q uare foot 
per minute. 

1 kilogram-me¬ 
ter. 


1 pound of car¬ 
bon oxidized 
with perfect 
efficiency. 


1.356 joules. 

0.1383 kilogram-meter. 

0.000000377 kilowatt-hour. 

0.001285 heat units. 

0.0000005 horsepower-hour. 

1 joule per second. 

0.00134 horsepower. 

3.412 heat units per hour. 

0.7373 foot-pound per second. 
0.0035 pound of water evaporated 
per hour. 

44.24 foot-pounds per minute. 

8.19 heat units per square foot per 
minute. 

6,371 foot-pounds per square foot 
per minute. 

0.193 horsepower per square foot. 
1,055 watt-seconds. 

778.6 kilogram-meters. 

0.000293 kilowatt-hour. 

0.000393 horsepower-hour. 

0.0000688 pound of carbon oxidized. 
0.001036 pound of water evapo¬ 
rated from and at 212° F. 

0.122 watt per square inch. 

0.0176 kilowatt per square foot. 
0.0236 horsepower per square foot. 
7.233 foot-pounds. 

0.00000365 horsepower-hour. 
0.00000272 kilowatt-hour. 

0.0093 heat unit. 

14,544 heat units. 

1.11 pounds of anthracite coal oxi¬ 
dized. 

2.5 pounds of dry wood oxidized. 
21 cubic feet of illuminating gas. 


4.26 kilowatt-hours. 


1 pound of wa¬ 
ter evapor¬ 
ated from 
and at 212° F. 


5.71 horsepower-hours. 

11,315,000 foot-pounds. 

15 pounds of water evaporated 
from and at 212° F. 

0.283 kilowatt-hour. 

0.379 horsepower-hour. 

965.7 heat units. 

103,900 kilogram-meters. 

1,019,000 joules. 

751,300 foot-pounds. 

0.0664 pound of carbon oxidized. 


LAWS OF ELECTRICAL RESISTANCE. 

The resistance, R, of any conductor varies directly as its length, l, and inversely 
as its section area, s, or R col-v-s. 

If r — the resistance of a conductor 1 unit in length and 1 square unit in sectional 
area, R=rl-*-s. The common unit of length for electrical calculations in English meas¬ 
ure is the foot, and the unit of area of wires is the circular mil, which equals the area 
of a circle 0.001 inch in diameter. One mil-foot is equivalent to an object 1 loot 
long and 1 circular mil in cross section. Resistance of 1 mil-foot of soft copper wire at 
51 ° F. = 10 international ohms. 

Example .—What is the resistance of a wire 1,000 feet long and 0.1 inch in diameter? 

0.1 inch in diameter= 10,000 circular mils. 

tf=W-us=10Xl,000-f-10,000=l ohm. 
























188 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Specific resistance, also called resistivity, is the resistance of a material of unit 
length and section as compared with the resistance of soft copper. 

Conductivity is the reciprocal of specific resistance, or the relative conducting 
power compared with copper taken at 100. 

Electrical conductivity of different metals and alloys. 


Pure silver. 100 

Pure copper. 100 

. Telegraphic siliceous bronze. 98 

Alloy of one-half copper and one-half silver.. 86.65 

Pure gold. 78 

Silicide of copper, 4 per cent Si. 75 

Telephonic siliceous bronze. 35 

Pure zinc. 29.9 

Brass with 35 per cent zinc. 21.5 

Phosphor tin. 17.7 

Alloy of one-half gold and one-half silver.... 16.12 


Swedish iron. 16 

Pure Banca tin. 15. 45 

Aluminum bronze (10 per cent). 12.6 

Siemens steel. 12 

Pure platinum. 10.6 

Copper with 10 per cent nickel. 10.6 

Pure lead. 8.88 

Bronze with 20 per cent tin. 8. 4 

Pure nickel. 7.89 

Phosphor bronze, 10 per cent tin. 6.5 

Antimony. 3.88 


Conductivity of aluminum. —J. W. Richards (Jour. Franklin Inst., Mar., 1897) 
gives for hard-drawn aluminum of purity 98.5, 99, 99.5, and 99.75 per cent, respectively, 
a conductivity of 55, 59, 61, and 63 to 64 per cent, copper being 100 per cent. The 
Pittsburgh Reduction Co. claims that its purest aluminum has a conductivity of 
over 64.5 per cent. (Eng. News, Dec. 17, 1896.) 

German silver. —The resistance of German silver depends on its composition. Matth- 
iessen gives it as nearly 13 times that of copper, with a temperature coefficient of 
0.0004433 per degree centigrade. Weston, however (Proc. Electrical Cong.. 1893, 
p. 179), has found copper-nickel-zinc alloys (German silver) that had a resistance of 
nearly 28 times that of copper and a temperature coefficient of about one-half that 
given by Matthiessen. 

Conductors and insulators in order of their value. 


All metals. 

Well-burned charcoal. 
Graphite. 

Acid solutions. 

Saline solutions. 


Dry air. 

Shellac. 

Paraffin. 

Amber. 

Resins. 

Sulphur. 

Wax. 


CONDUCTORS. 

Metallic ores. 

Animal fluids. 

Living vegetable substances. 
Moist earth. 

Water. 

INSULATORS (NONCONDUCTORS). 

Ebonite. 

Gutta percha. 

India rubber. 

Silk. 

Dry paper. 

Parchment. 

Dry leather. 


Jet. 

Glass. 

Mica. 

Porcelain. 

Oils. 


According to Culley, the resistance of distilled water is 6,754 million times as great 
as that of copper. Impurities in water decrease its resistance. 


RESISTANCE VARIES WITH TEMPERATURE. 


For every degree centigrade, the resistance of copper increases about 0.4 per cent, 
or for every degree Fahrenheit, 0.2222 per cent. Thus, a piece of copper wire having 
a resistance of 10 ohms at 32° would have a resistance of 11.11 ohms at 82° F. 

The following table shows the amount of resistance of a few substances used for 
various electrical purposes by which 1 ohm is increased by a rise of temperature of 
1° C. 


Platinoid. 0.00021 

Platinum silver.00031 

German silver.00044 


Gold, silver. 0.00065 

Cast iron.00080 

Copper.00400 































GLOSSARY. 


189 


ohm’s law. 

» 

This law expresses the relation between the three fundamental units of resistance, 
electrical pressure, and current. It is: 

Current=—- ctric . a * P re93ure ; /_f • whence E=IR and B-* 
resistance R / 

In terms of the units of the three quantities, 

Amperes=- °^ 8 ; volts=amperesXohms; ohms=- vo ^ s . 

ohms r ’ amperes 

EXAMPLES. 

1. If the source has an effective electrical pressure of 100 volts, and the resistance is 
2 ohms, what is the current? 

T E 100 

i=^==-=-=50 amperes 
R 2 

2. What pressure will give a current of 50 amperes through a resistance of 2 ohms? 

E=IR=b0X2=100 volts. 

3. What resistance is required to obtain a current of 50 amperes when the pressure 
is 100 volts? 

R—E-i-T— 100-^50=2 ohms. 

Ohm’s law applies equally to a complete electrical circuit and to any part thereof. 

HEAT GENERATED BY A CURRENT. 

Joule’s law shows that the heat developed in a conductor is directly proportional, 
first, to its resistance; second, to the square of the current strength; and, third, to the 
time during which the current flows, or H=PRt. Since I=E-i-R, 

PRt = ~IRt—Elt—E^=~^ 

R R R 

Or, heat=current 2 X resistance X time 

=electromotive force X current X time 
=electromotive force 2 X time-4-resistance 
Q =quantity of electricity flowing =It, or ( Et-i-R ) 

H=EQ, or lieat=electromotive forceXquantity. 

The electromotive force here is that causing the flow, or the difference in potential 
between the ends of the conductor. 

The electrical unit of heat or “joule ” equals 10 7 ergs, equals heat generated in 1 second 
by a current of 1 ampere flowing through a resistance of 1 ohm, equals 0.239 gram of 
water raised 1° C. H=PRtX0.239 gram calories=/ 2 i^X0.0009478 British thermal 
unit. 

In electric lighting the energy of the current is converted into heat in the lamps. 
The resistance of the lamp is made great so that the required quantity of heat may be 
developed, while in the wire leading to and from the lamp the resistance is made as 
small as is commercially practicable, so that as little energy as possible may be wasted 
in heating the wire. 


I 







SELECTED BIBLIOGRAPHY. 


BOOKS. 

Ashcroft, E. A. Study of electrothermal and electrolytic industries. New York, 
1909. Intended to supply information about all industrially successful electro¬ 
chemical and electrometallurgical industries. 

Borchers, W. Electric furnaces; the production of he^t from electrical energy, 
and the construction of electric furnaces. Translated by H. G. Solomon, London, 
1908. 

Guillet, S. Etude industriel des alliages metallique. Paris. 

Haanel, E. Report of commission appointed to investigate different electrothermic 
processes for smelting iron ores and making steel in Europe. Canada, Depart¬ 
ment of the Interior, Mines Branch, 1904. 

- Report on electric shaft furnace at Domnarfvet, Sweden. Canada, Depart¬ 
ment of the Interior, Mines Branch, 1909. 

- Recent advances in electric smelting. Bulletin No. 3, Canada, Department. 

of the Interior, Mines Branch, 1910. 

- Report on experiments at Sault Sainte Marie, Ontario, under government 

auspices on smelting of Canadian iron ores by the electrothermic process. Can¬ 
ada, Department of the Interior, Mines Branch, 1907. 

Havard, F. T. Refractories and furnaces. New York, 1912. 

Ingalls, W. R. The metallurgy of zinc. 

Kershaw, J. B. C. Electrometallurgy. London, 1908. 

Minet, A. The production of aluminium and its industrial use. Translated with 
addition by L. Waldo, New York, 1905. 

Moissan, H. The electric furnace. Translated by Y. Lenher, 1904. 

Neumann, B. Elektrometallurgie des Eisens, W. Knapp, Halle, Germany, 1907. 

Robin, F. Traite de Metallographie. Paris, 1912. 

Rodenhauser, W., and Schoenawa, I. Electric furnaces in the iron and steel 
industry. Translated by C. H. Yom Baur. 1913. 

Stansfield, A. The electric furnace, its evolution, theory, and practice. New 
York, 1907. 

Thompson. M. he Kay. Applied electrochemistry. New York, 1911. 

Wright, J. Electric furnaces and their industrial applications. New York, 1904. 

PUBLISHED PAPERS AND ARTICLES. 

ALUMINUM. 

Burgess, C. F., and Hambuechen, C. Some laboratory observations on aluminum. 
Electrochem. Ind., vol. 1, 1902, p. 165. 

Engineering and Mining Journal. Electric reduction of aluminum. Vol. 93, 

1912, p. 641. 

Hambuechen, C. See Burgess, C. F. 

Hutton, R. S., and Petavel, J. E. On direct reduction of alumina with carbon. 
Electrochem. and Met. Ind., vol. 6, 1908, p. 104. 

Mineral Industry. Aluminum. Vol. 19, 1910, p. 18, vol. 20, 1911, p. 22. 

Neumann, B., and Ollsen, H. Production of aluminium as a laboratory experiment. 
Met. and Chem. Eng., vol. 7, 1910, p. 185. 

Ollsen, H. See Neumann, B. 

Petavel, J. E. See Hutton, R. S. 

190 





SELECTED BIBLIOGRAPHY. 


191 


Richards, J. W. Present metallurgy of aluminium. Electrochem. Ind., vol 1, 
1902, p. 158. 

Aluminium nitride. Trans. Am. Electrochem Soc., vol. 23, 1913, p. 351. 
Richardson, H. Some observations on laboratory production of aluminium. Trans. 

Am. Electrochem. Soc., vol. 19, 1911, p. 159. 

Thompson, M. de Kay. The electrolytic reduction of aluminium as a laboratory 
experiment. Electrochem. and Met. Ind., vol. 7, 1909, p. 14. 

Tucker, S. A. The preparation of aluminium in the laboratory. Electrochem. and 
Met. Ind., vol. 7, 1909, p. 315. 

ARC FURNACE. 

Alexander, W . A., Tucker, S. A., and Hudson, H. K. Relative efficiency of the 
arc and resistance furnace for the manufacture of calcium carbide. Trans. Am. 
Electrochem. Soc., vol. 15, 1909, p. 411. 

Hansen, C. A. Small experimental H^roult furnace. Electrochem. and Met. Ind., 
vol. 7, 1909, p. 206. 

Hudson, H. K. See Alexander, W. A. 

Thompson, M. de Kay. Preparation and properties of calcium carbide. Trans. Am. 
Electrochem. Soc., vol. 16, 1909, p. 197. 

Tone, F. T. Production of silicon in the electric furnace. Trans. Am. Electrochem. 
Soc., vol. 7, 1905, p. 243. 

Tucker, S. A. The preparation of silicon in the laboratory. Met. and Chem. Eng., 
vol. 8, 1910, p. 19. 

- See also Alexander, W. A. 

Weedon, W. S. A contribution to the study of the electric arc. Trans. Am. Elec¬ 
trochem. Soc., vol. 5, 1904, p. 171. 

- The titanium arc. Trans. Am. Electrochem. Soc., vol. 16, 1909, p. 217. 

Whitney, W. R. Arcs. Trans. Am. Electrochem. Soc., vol. 7, 1905, p. 291. 

CALCIUM AND MAGNESIUM. 

Badger, W. L., and Frary, F. 0. The preparation of calcium. Trans. Am. Electro¬ 
chem. Soc., vol. 15, 1909, p. 185. 

Bicknell, H. R., Frary, F. C., and Tronson, C. A. Efficiency in the electrolytic 
production of metallic calcium. Trans. Am. Electrochem. Soc., vol. 18, 1910, 
p. 117. 

Frary, F. C. See Badger, W. L.; also Bicknell, H. R. 

Johnson, A. R. The electrolytic preparation of calcium. Trans. Am. Electrochem. 
Soc., vol. 18, 1910, p. 125. 

Jouard, F. L., and Tucker, S. A. The electrolytic preparation of magnesium. 

Trans. Am. Electrochem. Soc., vol. 17, 1910, p. 249. 

Tronson, C. A. See Bicknell, H. R. 

Tucker, S. A. See Jouard, F. L. 

COPPER. 

• 

Haanel, E. Report of the commission appointed to investigate the different elec- 
trothermic processes for the smelting of iron ores and the making of steel in opera¬ 
tion in Europe. Canada, Department of Interior, Mines Branch, 1904. Report 
on electric copper smelting by Vatier. 

Keeney, R. M., and Lyon, D. A. The smelting of copper ores in the electric furnace. 
Am. Inst. Min. Eng., No. 80, Aug., 1913, p. 2151; Met. and Chem. Eng., vol. 11, 
1913, p. 522. 

Lyon, D. A. See Keeney, R. M. 

Richards, J. W. Metallurgical calculations. Electric smelting of copper ores. 
Electrochem. and Met. Ind., vol. 5, 1907, p. 496. 

- The electric furnace in nonferrous metallurgy. Met. and Chem. Eng., vol. 8, 

1910, p. 233. 






192 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Schilowski, J. La fusion 61ectrique de cuivre et des produits intermediares de 
fonderies de cuivre. Rev. de M6t., vol. 9,1912, p. 205. 

Stephan, M. Einiges liber die Erzeugung von Metallen im elektrischen Ofen. 
Metall. und Erz., vol. 1, 1912, p. 11. 

Weeks, C. A. Melting nonferrous metals in an electric furnace. Met. and Chem. 
Eng., vol. 9, 1911, p. 363. 

Wolkoff, W. Electric smelting of copper sulphide ores. Metallurgie, vol. 7, 1910, 
p. 99. 

ELECTRODES. 

Clocher, W. Manufacture of carbons. Met. and Chem. Eng., vol. 9, 1911, p. 137. 
Collens, C. L. Graphite electrodes in electrometallurgical processes. Trans. Am. 
Electrochem. Soc., vol. 1, 1902, p. 53. 

Fitzgerald, F. A. J. On testing of carbon electrodes. Trans. Am. Electrochem. 
Soc., vol. 2, 1902, p. 43. 

- On carbons for electrometallurgy. Trans. Am. Electrochem. Soc., vol. 11, 

1907, p. 317. 

Fitzgerald, F. A. J., and Hinckley, A. T. Experiments with furnace electrodes. 

Trans. Am. Electrochem. Soc., vol. 23, 1913, p. 333. 

Forsell, J. Current densities and energy losses in electrodes. Met. and Chem. 
Eng., vol. 8, 1910, p. 26. 

Hansen, C. A. Furnace electrode losses. Trans. Am. Electrochem. Soc., vol. 15, 

1909, p. 279; vol. 16, 1909, p. 329. 

-Furnace electrode losses. Electrochem. and Met. Ind., vol. 7, 1909, pp. 358, 

389. 

Hering, C. Laws of electrode losses in electric furnaces. Trans. Am. Electrochem. 
Soc., vol. 16, 1909, p. 265. 

- A new method of measuring mean thermal and electrical conductivities of 

furnace electrodes. Trans. Am. Electrochem. Soc., vol. 16, 1909, p. 317. 

— -- Determination of the constants of materials for furnace electrodes. Trans. 

Am. Electrochem. Soc., vol. 17, 1910, p. 151. 

———- Empirical laws of furnace electrodes. Trans. Am. Electrochem. Soc., vol. 17, 

1910, p. 171. 

- Method for determining thermal conductivities. Trans. Am. Electrochem. 

Soc., vol. 18, 1910, p. 213. 

- Furnace electrode losses. Electrochem. and Met. Ind., vol. 7, 1909, p. 400. 

— - Properties and behavior of furnace electrodes. Met. and Chem. Eng., vol. 7, 

1909, p. 442; Discussion, vol. 9, 1910, pp. 42, 67, 665; vol. 10, 1910, pp. 128, 154, 
206. 

- Electrode efficiency of furnaces. Electrochem. and Met. Ind., vol. 7, 1909, 

p. 473. 

- Chilling and heating of electrodes. Met. and Chem. Eng., vol. 8, 1910, p. 

188. 

- Electrode design. Proc. Am. Inst. Elec. Eng., vol. 29, 1910, p. 285. 

Hering, C., and Kennelly, A. E. Furnace electrode losses. Met. and Chem. Eng., 
vol. 8, 1910, p. 238. 

Hinckley, A. T. See Fitzgerald, F. A. J. 

Kennelly, A. E. The modification in Hering’s law of electrodes by including varia¬ 
tions in electric and thermal resistivity. Proc. Am. Inst. Elec. Eng., vol., 29, 

1910, p. 465. 

- Electrode-holder construction for electric furnaces. Met. and Chem. Eng., 

vol. 11, 1913, p. 321. 

- Manufacture of carbon electrodes. Met. and Chem. Eng., vol. 9, 1911, pp. 

42, 67, 111, 137, 221, 377, 559, 665. 

- Production of electrodes. Met. and Chem. Eng., vol. 8, 1910, p. 291. 

- See also Hering, C. 

















SELECTED BIBLIOGRAPHY. 


193 


Moissan, H. Electrodes. Compt. Rend., vol. 135, p. 1902. 

Roeber, E. F. Electrode losses in electric furnaces. Trans. Am. Electrochem. Soc., 
vol. 16, 1909, p. 363. 

Roush, G. A. Manufacture of carbons for steel furnaces. Jour. Ind. and Eng. Chem., 
vol. 1, 1909, p. 286. 

Turnbull, R. Furnace electrodes practically considered. Trans. Am. Electrochem. 
Soc., vol. 21, 1912, p. 397. 

ELECTROMECHANICAL FORCES. 

Harden, J. The “pinch” effect in electric furnaces of the induction type. Electro¬ 
chem. and Met. Ind., vol. 7, 1909, p. 478. 

Hering, C. Formulas for the pinch phenomenon. Met. and Chem. Eng., vol. 9, 

1911, p. 86. 

- A practical limitation of resistance furnaces; the pinch phenomenon. Trans. 

Am. Electrochem. Soc., vol. 21, 1907, p. 329. 

- The working limit in electric furnaces due to the “pinch” phenomenon. 

Trans. Am. Electrochem. Soc., vol. 15, 1909, p. 255. 

- A new type of electric furnace. Trans. Am. Electrochem. Soc., vol. 19, 1911, 

p. 255. 

- Electric furnaces for molten materials. Met. and Chem. Eng., vol. 9, 1911, 

p. 37; Trans. Am. Electrochem. Soc , vol. 19, 1911, p. 255. 

- An imperfection in the usual statement of the fundamental law of electro¬ 
magnetic induction. Proc. Am. Inst. Elec. Eng., vol. 27, 1908, p. 134. 
Northrup, E. F. Some newly observed manifestations of forces in the interior of an 
electric conductor. Physical Rev., vol. 24, No. 6, 1907, p. 474. 

Scott, E. K. The Hering “pinch-effect” furnace. Trans. Faraday Soc., vol. 7, 

1912, p. 202. 

Unger, M. The action of electromechanical forces in the bath of an induction fur¬ 
nace. Met. and Chem. Eng., vol. 10, 1912, p. 263. 

ELECTROLYSIS. 

Ashcroft, E. A. Factory scale experiments with fused electrolytes. Electrochem. 

and Met. Ind., vol. 4, 1906, pp. 143, 178, and 357. 

Beekman, J. W. An electrolytic furnace method for producing metals. Trans. Am. 
Electrochem. Soc., vol. 19, 1911, p. 171. 

Burgess, C. F. Electrolytic refining as a step in the production of steel. Trans. 

Am. Electrochem. Soc., vol. 19, 1911, p. 181. 

Chance, E. M. A new method for the electrolytic winning and refining of metals. 

Trans. Am. Electrochem. Soc., vol. 17, 1910, p. 235. 

Goodwin, H. M., and Mailey, R. D. On the density, electrical conductivity, and 
viscosity of fused salts.. Trans. Am. Electrochem. Soc., vol. 11, 1907, p. 211. 
Mailey, R. D. See Goodwin, H. M. 

FERRO-ALLOYS. 

Ballagh, J. C., and Iwai, K. Investigation of ferroboron. Min. and Sci. Press, vol. 
99, 1909, p. 185. 

Bennett, S. R., Copeman, S. M., and Hahe, H. W. Manufacture and transport of 
ferrosilicon. Yellow book of British Local Government Board; Met. and Chem. 
Eng., vol. 8, 1910, p. 133; Iron and Coal Trades Rev., vol. 80, 1910, p. 45. 
Carnot, and Goutal. Recherches sur Petat ou se trouvent le silicium et le chrome 
dans les produits siderurgiques. Compt. Rend., vol. 126, 1898, p. 1240. 

Catani, R. The application of electricity in the metallurgy of Italy. J our. Iron and 
Steel Inst., vol. 84, No. 2, 1911, p. 215; Met. and Chem. Eng., vol. 9, 1911, p. 642. 
Chaplet, M. Les alliages ferrometalliques, Rev. de Met., vol. 6, 1909, p. 739. 







194 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Conrad, W. Electric furnaces for the manufacture of calcium carbide and ferro- 
silicon. Electrochem. and Met. Ind., vol. 6, 1908, p. 397. 

Conrad, W., and Pick, W. Die Herstellung von Hochprozentigem Ferrosilizium im 
elektrischen Ofen. Pub. by W. Knappe, Halle, Germany, 1909; Rev. de Met., 
vol. 9, 1912, p. 362. 

Copeman, S. M. See Bennett, S. R. 

Electrochemical Industry. Ferrosilicon made in the electric furnace. Vol. 2, 
1904, p. 122. 

Electrochemical and Metallurgical Industry. Ferro-alloys. Vol. 4, 1906, p. 
247. 

Engineer (London). The manufacture and use of ferro-alloys. Vol. 105, 1908, 
pp. 80 and 105. 

Escard, M. Ferrosilicium. La Lumiere Electrique. Mar. 6, 1909. 

Genie Civil. La fabrication du ferromanganese en France. Feb. 10, 1906. 

Gin, G. Decarburization of ferro-alloys. Trans. Am. Electrochem. Soc., vol. 15, 
1909, p. 225. 

- Ferrosilicium. L’Eclairage Electrique, vol. 27, May 4, 1900. 

- Memoirs on the methods of treatment of simple and complex ores of molyb¬ 
denum, tungsten, uranium, and vanadium. Trans. Am. Electrochem. Soc., 
vol. 12, 1907, p. 411; vol. 13, 1908, p. 481; vol. 16, 1909, p. 393. 

- Note upon the manufacture of silicovanadium. Trans. Am. Electrochem. 

Soc., vol. 15, 1909, p. 229. 

-- Preparation of ferrovanadium by electrolysis. Trans. Am. Electrochem. 

Soc., vol. 15, 1909, p. 227. 

Girod, P. Les alliages ferrometalliques. Soeiete des Ingeneurs Civils de France, 
Nov., 1906. 

Goutal, see Carnot. 

Greenwood, H. C., Slade, R. E., and Pring, J. N. Reduction of refractory oxides, 
production of ferro-alloys, and formation of carbides. Trans. Chem. Soc., vol. 93, 
1908, p. 1484, Electrochem. and Met. Ind., vol. 7, 1909, p. 119. 

Guichard, M. Production of molybdenum from molybdenite. Compt. Rend., 
vol. 122, p. 1270. 

Hadfield, R. A. Alloys of iron and tungsten. Jour. Iron and Steel Inst., vol. 64, 
No. 2, 1903, p. 14. 

Hahe, H. W., see Bennett, S. R. 

Haughton, E. Ferro-alloys in the foundry. Electrochem. and Met. Ind., vol. 5, 
1907, p. 9. 

Hutton, R. S. Recent advances in the electrometallurgy of iron and steel. Soc. 
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Iron Trade Review. Ferrovanadium. Vol. 51, 1912, p. 275. 

I wai, K. See Ballagh, J. C. 

Jakoki, J. Ferromanganese in Hochofen. Stahl und Eisen., vol. 29, 1909, p. 1191. 

Keeney, R. M. The production of steels and ferro-alloys directly from ore in the 
electric furnace. Jour. Iron and Steel Inst., vol. 4, 1912, p. 108. 

- Electric smelting of chromium, tungsten, molybdenum, and vanadium ores. 

Trans. Am. Electrochem Soc., vol. 24, 1913, p. 167; Met. and Chem. Eng., vol. 

11, 1913, p. 585. 

Keeney, R. M., and Lee, G. M. The direct production of steels and ferro-alloys from 
ore in the electric furnace. West. Chem. and Metal, vol. 6, 1910, pp. 269, 323, 
347. 

Keeney, R. M., and Lyon, D. A. Possible application of the electric furnace to 
western metallurgy. Trans. Am. Electrochem. Soc., vol. 24, 1913, p. 119; Met. 
and Chem. Eng., vol. 11, 1913, p. 577. 







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Keller, C. A. The electric furnace and the manufacture of ferro-alloys. Jour. Iron 
and Steel Inst., vol. 63, 1903, No. 1, p. 162. 

Lebeau, P. Sur les gas toxiques degagee par les ferrosilicium sous Paction Pair 
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Lee, G. M. See Keeney, R. M. 

Lehner, W. Herstellung von Molybdenum. Metallurgie, vol. 3, 1906, p. 549. 

Louis, J. La fabrication des ferrosilicium au four electrique. Jour, du Four Elec- 
rique et de Lumiere, Oct. 1, 1910, p. 415. 

Lyon, D. A. See Keeney, R. M. 

Metallurgical and Chemical Engineering. Electric smelting of nickel ore Yol 
8, 1910, p. 277. 

-Swedish methods of packing ferrosilicon. Vol. 11, 1913, p. 87. 

Moissan, H. Compt. Rend., vol. 121, p. 621. 

Morrison, W. L. Electric-furnace treatment of nickel ore and the development of a 
commercial process. Trans. Am. Electrochem. Soc., vol. 20, 1911, p. 315; Met. 
and Chem. Eng., vol. 9, 1911, p. 546. 

Neumann, B. Herstellung von Ferro-liegierung im elektrischen Ofen. Stahl und 
Eisen, vol. 28, 1908, p. 356. 

Pick, W. See Conrad, W. 

Petavel. Ferrosilicium. Journal d’Electrolyse, vol. 3, June 3, 1904. 

Pratt, L. R. Manufacture of metallic tungsten and ferrotungstcn in the crucible. 
Electrochem. and Met. Jour., vol. 90, 1910, p. 959. 

Pring, J. N. See Greenwood, H. C. 

Rossi, A. J. Ferro-alloys. Min. Ind., vol. 12, 1903, p. 693. 

- Exhibit of ferrometals made electrically, and of other electric-furnace pro¬ 
ducts. Trans. Am. Electrochem. Soc., vol. 5, 1904, p. 275. 

•- On the manufacture of ferro-alloys in general and of ferrotitanium in par¬ 

ticular in the electric furnace. Electrochem. Ind., vol. 1, 1903, p. 523. 

Scholl, G. P. Manufacture of ferro-alloys in the electric furnace. Electrochem. 
Ind., vol. 2, 1904, pp. 349, 395, 449. 

Scroeder, F. Remelting of ferromanganese in the electric furnace and the use of 
molten ferromanganese for deoxidization. Met. and Chem. Eng., vol. 9, 1910, 
p. 640. 

Sjostedt, E. A. Electric-smelting experiments for the manufacture of ferronickel 
from pyrrhotite. Trans. Am. Electrochem. Soc., vol. 5, 1904, p. 233. 

Slade, R. E. See Greenwood, H. C. 

Slocum, C. V. Titanium in iron and steel. Trans. Am. Electrochem. Soc., vol. 20, 
1911, p. 265. 

Stansfield, A. The electrothermic production of steel from iron ore. Trans. Can. 
Min. Inst., vol. 10, 1907, p. 128. 

.-Tool steel direct from ore in an electric furnace. Trans. Can. Min. Inst., 

vol. 13, 1910, p. 151. 

Stassano, E. Treatment of iron and steel in the electric furnace. Electrochem. 
and Met. Ind., vol. 6, 1908, p. 35. 

Steinhart, D. J. Notes on metals and their ferro-alloys used in the manufacture 
of alloy steels. Inst. Min. and Met., vol. 15, 1905; p. 228; Min. Jour., 1906, p. 128. 

Stephan, M. Einiges iiber die Erzeugung von Metallen im elektrischen Ofen. 
Metall. und Erz, vol. 1, 1912, p. 11. 

Taussig, R. Large electric furnace. Trans. Faraday Soc., vol. 5, 1909, p. 254. 

.- Present status of the development of large electric furnaces. Met. and Chem. 

Eng., vol. 10, 1912, p. 686. 

Venator, W. Ueber Eisen Legierungen und Metall fur die Stahl Industrie. Stahl 
und Eisen, vol. 28, 1908, p. 41; Iron and Coal Trades Rev., vol. 76, 1908, p. 520 

VVeintraub, E. Preparation and properties of pure boron. Trans. Am. Electrochem. 
Soc., vol. 16, 1909, p. 165. 







196 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


FURNACES. 

Adler, E., and Sabersky, E. A new electrical hardening furnace. Trans. Faraday 
Soc., vol. 5, 1909, p. 15. 

Fitzgerald, F. A. J. Experiments with an electrothermic muffle furnace. Elec- 
trochem. and Met. Ind., vol. 3, 1905, p. 135. 

—-—— The Borchers furnace. Electrochem. and Met. Ind., vol., 3, 1905, p. 215. 
- The Ruthenburg and Acheson furnaces. Electrochem. and Met. Ind., vol. 

3, 1905, p. 416. 

Harden, J. Some electric-furnace notes. Met. and Chem. Eng., vol. 9, 1911, p. 130. 
Johnson, W. McA. Rotary electric furnace. Electrochem. and Met. Ind., vol, 

4, 1906, p. 321. 

Sabersky, E. See Adler, E. 

Taylor, E. R. The manufacture of bisulphide of carbon in the electric furnace. 
Trans. Am. Electrochem. Soc., vol. 1, 1902, p. 115. 

—-- Some advances in the closed and continuous working electric furnace. Trans. 

Am. Electrochem. Soc., vol. 2, 1902, p. 185. 

■- A closed electric furnace for reducing and distilling metals from their ores. 

Trans. Am. Electrochem. Soc., vol. 11, 1907, p. 294. 

GENERAL DESCRIPTION. 

Bennie, P. McN. The electric furnace, its place in siderology. Trans. Can. Min. 
Inst., vol. 13, 1910, p. 135. 

Brown, O. W. The reduction of metal sulphides. Trans. Am. Electrochem. Soc., 
vol. 9, 1906, p. 109. 

Burgess, C. F. The present status of electric-furnace working. Jour. West. Soc. 
Eng., vol. 10, 1905, p. 16. 

Catani, R. The application of electricity in the metallurgy of Italy. Jour. Iron 
and Steel Inst., vol. 84, No. 2, 1911, p. 215; Met. and Chem. Eng., vol. 9, 1911, 
p. 642. 

Dushman, S. Electrochemical and electrometallurgical developments in Canada. 

Trans. Am. Electrochem. Soc., vol. 20, 1911, p. 419. 

Farnsworth, L. D. Experimental electric smelting. Electrochem. and Met. Ind., 
vol. 6, 1908, p. 326. 

Harden, J. Some electric-furnace notes. Met. and Chem. Eng., vol. 9, 1911, p. 130. 
Hering, C. Advantage of small high-speed electric furnaces. Met. and Chem. 
Eng., vol. 11, 1913, p. 183. 

-— Elementary principles of the design and operation of electric furnaces. Met. 

and Chem. Eng., vol. 8, 1910, p. 471. 

Hutton, R. S. On the fusion of quartz in the electric furnace. Trans. Am. Electro¬ 
chem. Soc., vol. 2, 1909, p. 105. 

Johnson, W. McA., and Sieger, G. N. Electric furnaces, their design, character¬ 
istics, and commercial application. Met. and Chem. Eng., vol. 11, 1913, pp. 504, 
563, 643. 

Keeney, R. M., and Lyon, D. A. Possible applications of the electric furnace to 
Western metallurgy. Trans. Am. Electrochem. Soc., vol. 24, 1913, p. 118. Met. 
and Chem. Eng., vol. 11, 1913, p. 577. 

Kowalke, O. L. Electric-furnace conversion of iron pyrites into a magnetic form. 

Trans. Am. Electrochem., Soc., vol. 13, 1908. p. 133. 

Kunye, W., Beitrag zum Entwicklungstand neulicher elektroofen. Stahl und 
Eisen, vol. 32, 1912, p. 1181. 

Louvrier, F. Electric heat vs. heat from fuel. Electrochem. and Met. Ind., vol. 5, 
1907, p. 298. 

- Electric and fuel furnaces compared. Electrochem. and Met. Ind., vol. 7, 

1909, p. 159. 








SELECTED BIBLIOGRAPHY. 


197 


Lyon, D. A. See Keeney, R. M. 

Metallurgical and Chemical Engineering. Editorial on the electric furnace 
and the scrap-metal business. Vol. 9, 1911, p. 620. 

Minet, A. The electric furnace; its origin, transformation, and applications. Trans 
Faraday Soc., vol. 1, 1905, p. 77; vol. 2, 1906, p. 1. 

Nernst, \\. Determination of vapor densities in an electric furnace. Trans. Am. 
Electrochem. Soc., vol. 3, 1903, p. 75. 

Richards, J. W. Conditions of progress in electrochemistry. Trans. Am. Electro¬ 
chem. Soc., vol. 3, 1903, p. 59. 

• - Electrochemistry at Sault Ste. Marie. Electrochem. Ind., vol. 1 , 1902, p. 85. 

■ - Furnace efficiency. Electrochem. Ind., vol. 1, 1902, p. 46. 

-- Niagara as an electrochemical center. Electrochem. Ind., vol. 1, 1902, p. 11. 

■ -— The efficiency of electric furnaces. Trans. Am. Electrochem. Soc vol 2 

1902, p. 51. 

• - The electrochemical industries of Norway. Trans. Am. Electrochem. Soc., 

vol. 20, 1911, p. 403. 

- The electric furnace in nonferrous metallurgy. Met. and-Chem. Eng., vol. 

8, 1910, p. 233. 

- What electrochemistry is accomplishing. Trans. Am. Electrochem. Soc., 

vol. 17, 1910, p. 75. 

Richards, J. W., and Hering, C. Efficiency—A discussion. Met. and Chem. Eng., 
vol. 9, 1911, p. 125. 

Ruthenburg, M. Electric smelting furnaces and their applications. Trans. Am. 

Electrochem. Soc., vol. 18, 1910, p. 185. 

Sieger, G. N. See Johnson, W. McA. 

Snyder, F. T. The reliability of electric furnaces for commercial work. Trans. Am. 
Electrochem. Soc., vol. 19, 1911, p. 185. 

Wellman, S. F. Discussion of the electric furnace. Iron Trade Rev., vol. 50, 1912, 
p. 1224. 

GOLD AND SILVER. 

Conklin, H. R. Electric furnace at Lluvia de Oro. Eng. and Min. Jour., vol. 93, 
1912, p. 1189. 

HEAT LOSSES. 

Clement, J. K., and Egy, W. L. Measurement of thermal conductivity of fire clay 
Bull. 36, Eng. Exper. Sta., University of Illinois. 

Egy, W. L. See also Clement, J. K. 

Electrochemical and Metallurgical Industry. Heating furnace walls to reduce 
heat losses. Vol. 7, 1909, p. 494. 

Fitzgerald, F. A. J. Experiments on heat insulation. Trans. Am. Electrochem. 
Soc., vol. 21, 1912, p. 535. 

- Heat losses in furnaces. Trans. Am. Electrochem. Soc., vol. 22, 1912, p. 111. 

- Heat losses of the electric furnace. Met. and Chem. Eng., vol. 9, 1911, p. 

1270. 

- On the heat conductivity of carbon. Trans. Am. Electrochem. Soc., vol. 

12, 1907, p. 165. 

- The use of carbon for the study of temperatures in the electric furnace. 

Trans. Am. Electrochem. Soc., vol. 6, 1904, p. 32. 

Hering, C. Effects of the variations of thermal resistivities with the temperature. 
Trans. Am. Electrochem. Soc., vol. 21, 1912, p. 511. 

- Heat conductance and resistance of composite bodies. Electrochem. and 

Met. Ind., vol. 7, 1909, p. 11. 

- Heat conductance through walls of furnaces. Trans. Am. Electrochem. 

Soc., vol. 14, 1908, p. 215. 















198 the electric furnace in metallurgical work. 


Herring, C. Improving the output and efficiency of existing electric furnaces. 
Met. and Chem. Eng., vol. 8, 1910, p. 276. 

- Method for determining thermal conductivities. Trans. Am. Electrochem. 

Soc., vol. 18, 1910, p. 213. 

- The thermal insulation of furnace walls. Met. and Chem. Eng., vol. 10, 

1912, p. 97. 

Kreisinger, Henry. See Ray, W. T. 

Metallurgical and Chemical Engineering. Electric-furnace temperature regu¬ 
lation. Vol. 8, 1910, p. 96. 

Ray, W. T., and Kreisinger, Henry. The flow of heat through furnace walls. 
Bull. 8, Bureau of Mines, 1911, 32 pp. 

Randolph, C. P. The thermal resistivity of insulating materials. Trans. Am. Elec¬ 
trochem. Soc., vol. 21, 1912, p. 545. 

Saunders, L. E. Temperature measurements on the silicon carbide furnace. Trans. 

Am. Electrochem. Soc., vol. 21, 1912, p. 425. 

Snyder, F. T. The flow of heat through furnace walls. Trans. Am. Electrochem. 
Soc., vol. 18,1910, p. 235. 

INDUCTION FURNACE. 

Englehardt, V. Electric induction furnace for making steel. Electrochem. and 
Met. Ind., vol. 3, 1905, p. 294. 

- The induction furnace and its use in the steel industry. Electrochem. and 

Met. Ind., vol. 6, 1908, p. 143. 

Fitzgerald, F. A. J. Experiments on melting in the induction furnace. Electro¬ 
chem. and Met. Ind., vol. 7, 1909, p. 10. 

Gin, G. Mathematics of the induction furnace. Trans. Am. Electrochem. Soc., 
vol. 12, 1907, p. 97. 

Harden, J. Induction-furnace notes. Met. and Chem. Eng., vol. 11, 1913, p. 559. 
- Present status of the induction furnace. Met. and Chem. Eng., vol. 11, 

1913, p. 99. 

- The efficiency of induction furnaces. Electrochem. and Met. Ind., vol. 7, 

1909, p. 320. 

Hiarth, A. Design of a 30-ton induction electric furnace. Trans. Am. Electrochem. 
Soc., vol. 20, 1911, p. 293. 

Neumann, B., Rochling, W., and Rodenhauser, W. Induction furnace for three- 
phase currents. Electrochem. and Met. Ind., vol. 6, 1908, p. 458. 

LABORATORY FURNACES. 

Bard, E. F., and Calhane, D. F. An efficient electric furnace for high tempera¬ 
tures. Met. and Chem. Eng., vol. 10, 1912, p. 416. 

Calhane, D. F., see Bard, E. F. 

Electrochemical and Metallurgical Industry. Electric laboratory furnaces. 
Vol. 7, 1908, pp. 219, 222. 

- Laboratory furnaces. Vol. 6, 1909, p. 256. 

—- Rheostat for small electric furnaces. Vol. 7, 1909, p. 168. 

Fitzgerald, F. A. J. Electric laboratory furnace. Electrochem. and Met. Ind., 
vol. 3, 1906, p. 55. 

- Experiments with an electrothermic muffle furnace. Electrochem. and Met. 

Ind., vol. 3, 1905, p. 135. 

Hutton, R. S., and Patterson, W. H. Electrically heated carbon tube furnaces. 

Trans. Faraday Soc., vol. 1, 1905, p. 187. 

Patterson, W. H. See Hutton, R. S. 

White, G. R. Laboratory resistance furnace. Trans. Am. Electrochem. Soc., vol. 9, 
1906, p. 143. 










SELECTED BIBLIOGRAPHY. 


199 


PIG IRON. 

Bennie, P. McN. Electric-furnace pig iron in California. Trans. Am. Electrochem. 
Soc., vol. 15, 1909, p. 35. 

- Application of the electric furnace to the metallurgy of iron and steel. Elec¬ 
trochem. Ind., vol. 2, 1904, p. 307. 

Campbell, D. E. Progress in the electrometallurgy of iron and steel. Trans. Faraday 
Soc., vol. 7, 1912, p. 195. 

Carcano, F. E. The production of pig iron in the electric furnace and the industrial 
utilizations of pyrite residue. Electrochem. and Met. Ind., vol. 7, 1909, p. 155. 

Catani, R. Large electric furnaces in the electrometallurgy of iron and steel. Trans. 
Am. Electrochem. Soc., vol. 15, 1909; p. 159; Electrochem. and Met. Ind., vol. 7, 
1909, p. 268. 

—— Reduction of iron ore in the electric furnace. Electrochem. and Met. Ind., 
vol. 7, 1909, p. 153. 

Crawford, J. Progress of electric smelting at Heroult, California. Met. and Chem. 
Eng., vol. 11, 1913, p. 386. 

Electrochemical and Metallurgical Industry. Iron reduction at the “Soo” 
by the Heroult electric furnace process. Vol. 4, 1906, p. 124. 

- Electric iron and steel industry in Canada and in Sweden and Norway. Vol. 

7, 1909, p. 419. 

Frick, O. Electric reduction of iron ores with special reference to results obtained in 
electro-metals furnace at Trollhattan, Sweden, and Noble furnace at Heroult, Cali¬ 
fornia. Met. and Chem. Eng., vol. 9, 1911, p. 631. 

Gin, G. On the electrical reduction of titaniferous iron ores. Trans. Am. Electro¬ 
chem. Soc., vol. 11, 1907, p. 291. 

Greene, A. E., and MacGregar, F. S. On the electrothermic reduction of iron ores. 
Trans. Am. Electrochem. Soc., vol. 12, 1907, p. 65. 

Haanel, E. Investigation of an electric shaft furnace, Domnarfvet, Sweden. Trans. 
Faraday Soc., vol. 5, 1909, p. 306. 

-- Preliminary report on the experiments made at Sault Ste. Marie under Gov¬ 
ernment auspices on the smelting of Canadian iron ores by the electrothermic 
process. Trans. Faraday Soc., vol. 2, 1906, p. 120. 

•- The electric shaft furnace of the Aktiebolaget Elektrometall, Ludvika, Sweden. 

Trans. Am. Electrochem. Soc., vol. 15, 1909, p. 25. 

Harbord, F. W. Recent developments in electric smelting in connection with iron 
and steel. Trans. Faraday Soc., vol. 1, 1905, p. 140. 

Harden, J. Smelting iron ores in the electric furnace in comparison with blast-furnace 
practice. Electrochem. and Met. Ind., vol. 7, 1909, p. 16. 

Keeney, R. M., and Lyon, D. A. Possible applications of the electric furnace to west¬ 
ern metallurgy. Trans. Am. Electrochem. Soc., vol. 24, 1913, p. 118; Met. and 
Chem. Eng., vol. 11, 1913, p. 577. 

Keller, C. A. Contribution to the study of electric furnaces as applied to the manu¬ 
facture of iron and steel. Trans. Am. Electrochem. Soc., vol. 15, 1909, p. 87. 

- Electrothermics of iron and steel. Trans. Faraday Soc., vol. 2, 1906, p. 36. 

Leffler, J. A., and Nystrom, E. Electric furnace pig iron at Trollhattan. Met. 
and Chem. Eng., vol. 10, 1912, p. 413. 

Leffler, J. A., and Odelberg, E. The electric iron reduction plant at Trollhattan, 
Sweden. Met. and Chem. Eng., vol. 9, 1911, pp. 368, 459, and 505. 

Lyon, D. A. The electric furnace in the production of pig iron from ore. Met. and 
Chem. Eng., vol. 11, 1913, p. 15. 

_ The Noble Electric Steel Company’s plant. Trans. Am. Electrochem. Soc., 

vol. 15, 1909, p. 39. 

- The use of electric-furnace pig iron in the open-hearth furnace. Met. and 

Chem. Eng., vol. 10, 1912, p. 539. 

- See also Keeney, R. M. 


44713°—Bull. 77—16-14 












200 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Lyman, J. The electric furnace for the manufacture of iron and steel. Trans. Am. 

Electrochem. Soc., vol. 19, 1910, p. 193. 

MacGregar, F. S. See Greene, A. E. 

Neumann, B. Electric-furnace methods in iron and steel manufacture in compari¬ 
son with ordinary metallurgical processes. Electrochem. Ind., vol. 2,1904, p. 488, 
Nystrom, E. See Leffler, J. A. 

Odelberg, E. See Leffler, J. A. 

Richards, J. W. Discussion of the experiments made at Sault Ste. Marie on the 
electrical reduction of iron ores. Trans. Am. Electrochem. Soc., vol. 12, 1907, 

p. 81. 

- Electric reduction of iron ore. Jour. Franklin Inst., vol. 169,1910, p. 131. 

- Gas circulation in electric reduction furnaces. Trans. Am. Electrochem. 

Soc., vol. 21, 1912, p. 403. 

- Metallurgical calculations; the electrometallurgy of iron and steel. Electro¬ 
chem. and Met. Ind., vol. 5, 1907, p. 165. 

- The electrometallurgical revolution in iron and steel industry of Norway and 

Sweden. Proc. Eng. Soc. West. Pa., vol. 27, 1911, p. 125. 

- The electrothermic production of iron and steel, method and furnace. Jour. 

Franklin Inst.,*Vol. 164, 1907, p. 443; vol. 165, 1908, p. 47. 

- The electric-furnace reduction of iron ore. Trans. Am. Electrochem. Soc., 

vol. 15, 1909, p. 53. 

Robertson, T. D. Recent progress in electrical iron smelting in Sweden. Trans. 
Am. Electrochem., Soc., vol. 20, p. 375. 

Rossi, A. J. Electric-smelting and blast-furnace gases. Electrochem. and Met. 
Ind., vol. 3, 1904, pp. 150, 190. 

- Note on the utilization of blast-furnace gases in connection with the electric 

smelting of iron. Trans. Am. Electrochem. Soc., vol. 7, 1905, p. 199. 

Simpson, L. The electric reduction of iron ores and the conversion of iron into steel 
in an electric furnace. Electrochem. Ind., vol. 1, 1903, p. 277. 

Stansfield, A. Laboratory experiments on removing silicon and phosphorus in 
smelting iron ores. Trans. Can. Min. Inst., vol. 10, 1907, p. 128. 

Taylor, E. R. Contribution to the electric .smelting of iron ore. Trans. Am. 
Electrochem. Soc., vol. 16, 1909, p. 229. 

Yngstrom, L. Electric blast furnace at Domnarfvet, Sweden. Met. and Chem. 
Eng., vol. 8, 1910, p. 11. 

- Electric production of iron from iron ore at Domnarfvet. Engineering (Lon¬ 
don), vol. 109, 1910, pp. 206, 234. 

POWER. 

Ashcroft, E. A. The influence of cheap electricity on electrolytic and electrother¬ 
mal industries. Trans. Faraday Soc., vol. 4, 1908, pp. 134, 149. 

Crabtree, F. Possibilities of cheap power in the Pittsburgh district. Trans. Am. 
Electrochem. Soc., vol. 17, 1910, p. 95. 

Electrochemical and Metallurgical Industry. Regulation of current in elec¬ 
tric furnaces. Yol. 3, 1905, p. 9. 

Jones, A. J. Transforming stations of Niagara electrochemical and electrometallur¬ 
gical industries. Trans. Am. Electrochem. Soc., vol. 20, 1911, p. 455. 

Knesche, F. A. Electric smelting of ore in the United States (an investigation of 
the possibility of utilizing energy from waste fuels). Iron Trade Rev., vol. 48, 
1911, p. 65. 

Lucre, C. E. Power cost. Trans. Am. Electrochem. Soc., vol. 11, 1907, p. 339. 
Meyer, J. Electrochemical processes as station-load equalizers. Trans. Am. Elec¬ 
trochem. Soc., vol. 11, 1907, p. 369. 

- Power for electrochemical purposes. Trans. Am. Electrochem. Soc., vol. 14, 

1908, p. 377. 











SELECTED BIBLIOGRAPHY. 201 

* > 

Metallurgical and Chemical Engineering. The power problem for electrochemi¬ 
cal plants. Vol. 9, 1911, p. 384. 

Northrup, E. F. A new type of ammeter for the accurate measurement of alternat¬ 
ing currents above 1,000 amperes. Trans. Am. Electrochem. Soc., vol. 15, 1909, 
p. 303. 

Randall, K. C. A study in heavy alternating-current conductors for electric fur¬ 
naces. Trans. Am. Electrochem. Soc., vol. 17, 1910, p. 139. 

Scott-Hansen, A. Hydroelectric plants in Norway and their application to electro¬ 
chemical industries. Trans. Faraday Soc., vol. 7, 1911, p. 78. 

Simpson, L. Cost of electric power used in electric reduction works. Electrochem. 
Ind., vol. 2, p. 421. 

Sperry, E. A. Electrochemical processes as station-load equalizers. Trans. Am. 
Electrochem. Soc., vol. 9, 1906, p. 147. 

- Utilization of power stations for electrochemical and electrothermal processes 

during periods of low load. Trans. Am. Electrochem. Soc., vol. 14, 1908, p. 259. 

Sykes, W. Power supply to electric furnaces for refining iron and steel. Trans. Am. 
Electrochem. Soc., vol. 21, 1912, p. 383. 

W ilson, J. R. High-tension equipment for electrochemical plants. Trans. Am. 
Electrochem. Soc., vol. 21, 1912, p. 371. 

REFRACTORY MATERIALS. 

Bleininger, A. V., and Brown, G. H. Testing of clay refractories, with special 
reference to their load-carrying capacities. Bureau of Standards Technologic 
Paper 7, 1911, 78 pp. 

Brown, G. H. See Bleininger, A. Y. 

Journal of Industrial and Engineering Chemistry. Committee on specifica¬ 
tions for refractories of Institute of Gas Engineers. Vol. 4, 1912, p. 618. 

Fitzgerald, F. A. J. Refractory materials in electrical resistance furnaces. Elec¬ 
trochem. Ind., vol. 2, 1904, p. 439. 

Harbison-Walker Refractories Co. Refractories in furnace construction. Met. 
and Chem. Eng., vol. 8, 1910, p. 106. 

Kanolt, C. W. Melting points of fire bricks. U. S. Bureau of Standards Tech¬ 
nologic Paper 10, 1912, 17 pp. 

McLeod, D. L., Stansfield, A., and McMahon, J. W. The electrical resistivity of 
fire bricks at high temperatures. Trans. Am. Electrochem. Soc., vol. 22, 1912, 
p. 89. 

McMahon, J. W. See McLeod, D. L. 

Queneau, A. L., and Wolgodine, S. Conductivity, porosity, and gas permeability 
of refractory materials. Electrochem. and Met. Ind., vol. 7, 1909, p. 383. 

Rigg, G. Defects in refractory brick and their causes. Met. and Chem. Eng., 
vol. 8, 1910, p. 237. 

Stansfield, A. See McLeod, D. L. 

Wolgodine, S. See Queneau, A. L. 

RESISTANCE FURNACE. 

Alexander, W. A., Tucker, S. A., and Hudson, H. L. Relative efficiency of the 
arc and resistance furnace for the manufacture of calcium carbide. Trans. Am. 
Electrochem. Soc., vol. 15, 1909, p. 411. 

Cauchois, R. W., Doty, A., and Tucker, S. A. Granular-carbon resistors. Trans. 
Am. Electrochem. Soc., vol. 12, 1907, p. 171. 

Collens, C. L. Some principles of resistor-furnace design. Trans. Am. Electrochem. 

Soc., vol. 9, 1906, p. 31. 

Dempster, J. T. K. Alloys for resistors. Electrochem. and Met. Ind., vol. 8, 1910 
p. 14. 



202 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 

Electrochemical and Metallurgical Industry. The works of the Interna¬ 
tional Acheson Graphite Co. at Niagara Falls. Vol. 7, 1909, p. 187. 

Doty, A. See also Cauchois, R. W. 

Fitzgerald, F. A. J. A new electric resistance furnace. Trans. Am. Electrochem. 
Soc., vol. 19, 1911, p. 273; Met. and Chem. Eng., vol. 9, 1911, p. 259. 

-A new resistor furnace. Met. and Chem. Eng., vol. 8, 1910, p. 317. 

■- Industrial resistance furnaces. Electrochem. and Met. Ind., vol. 3, 1905, 

p. 297. 

- Materials for resistors. Electrochem. Ind., vol. 2, 1904, p. 490. 

- Miscellaneous accessories of resistor furnaces. Electrochem. and Met. Ind., 

vol. 3, 1905, p. 9. 

- Note on an unsuccessful furnace experiment. Trans. Am. Electrochem. 

Soc., vol. 20, 1911, p. 281. 

- Note on some theoretical considerations in the construction of resistance 

furnaces. Trans. Am. Electrochem. Soc., vol. 4, 1903, p. 9. 

- Refractory materials in electrical resistance furnaces. Electrochem. Ind., 

vol. 2, 1904, p. 439. 

- Resistance furnace for crucibles. Electrochem. and Met. Ind., vol. 3, 1905, 

p. 55. 

- Some first principles of electrical resistance furnaces. Electrochem. Ind., 

vol. 2, 1904, p. 342. 

- The carborundum furnace. Electrochem. and Met. Ind., vol. 4, 1906, p. 53. 

Goodwin, J. H. Granular-carbon resistance furnaces. Met. and Chem. Eng., vol. 
9, 1911, p. 188. 

Hering, C. A new type of electric furnace. Trans. Am. Electrochem. Soc., vol. 
19, 1911, p. 255. 

- Electric furnaces for molten materials. Met. and Chem. Eng., vol. 9, 1911, 

p. 371. 

Heumann, E. M., Kudlich, H. F., and Tucker, S. A. The preparation of silundum. 

Trans. Am. Electrothem Soc., vol. 16, 1909, p. 207. 

Hudson, H. K. See Alexander, W. A. 

Kudlich, H. F. See Heumann, E. M. 

Tucker, S. A. See also Alexander, W. A.; Cauchois, R. W.; and Heumann, E. M. 
Watts, O. P. An electric furnace for heating crucibles. Electrochem. and Met. 
Ind., vol. 4, 1906, p. 273. 

STEEL. 

Amberg, R. Deoxidation and desulphurization in electric steel furnaces. Electro¬ 
chem. and Met. Ind., vol. 7, 1909, p. 115. 

- The function of slag in electric steel refining. Trans. Am. Electrochem. 

Soc., vol. 22, 1912, p. 133; Met. and Chem. Eng., vol. 10, 1912, p. 601. 

Arnou, M. G. Notes on the direct reduction of iron ores in the electric furnace. 
Rev. de Metal., vol. 7, 1910, p. 1190. 

Baily, T. F. An electric furnace for heating bars and billets. Trans. Am. Electro¬ 
chem Soc., vol. 19, 1911. p. 285. 

-Further development of electric furnace for heating bars and billets. Trans. 

Am. Electrochem. Soc., vol. 21, 1912, p. 419. 

Bennie, P. McN. Application of the electric furnace to the metallurgy of iron and 
steel. Electrochem. Ind., vol. 2, 1904, p. 307. 

Borchers, W. Electric smelting with the Girod furnace. Trans. Am. Inst. Min. 
Eng., vol. 41, 1910, p. 120. 

Bowman, R. G., and Dittus, E. J. The direct production of molybdenum steel in the 
electric furnace. Trans. Am. Electrochem. Soc., vol. 20, 1911, p. 355. 

Burg ss, 0. hi IClectrol\ tic refi.nin^ as a step in the production of steel. Trans. 
Am. Electrochem. Soc., vol. 19, 1911, p. 181. 















SELECTED BIBLIOGRAPHY. 


203 


Campbell, D. F. Electric steel refining. Jour. Iron and Steel Inst., vol. 82, No. 2, 
1910, p. 197. 

- Progress in the electrometallurgy of iron and steel. Trans. Faraday Soc., 

vol. 7, 1912, p. 195. 

Catani, It. Large electric furnaces in the electrometallurgy of iron and steel. Trans. 
Am. Electrochem. Soc., vol. 15, 1909, p. 159; Electrochem. and Met. Ind., vol. 7, 
1909, p. 268. 

The application of electricity in the metallurgy of Italy. Jour. Iron and Steel 
Inst., vol. 84, No. 2, 1911, p. 215; Met. and Chem. Eng., vol. 9, 1911, p. 642. 
Clark, C. B. Various types and applications of electric steel furnaces. Met. and 
Chem. Eng., vol. 10, 1912, p. 373. 

Dittos, E. J. See Bowman, R. G. 

Electrochemical and Metallurgical Industry. A Swiss electric-furnace steel plant. 
Vol. 6, 1908, p. 452. 

Electric iron and steel industry in Canada and in Sweden and Norway. Vol. 
7, 1909, p. 419. 

- Removal of sulphur in electric steel furnaces. Vol. 6, 1908, p. 405. 

- The electric furnace in iron and steel metallurgy. Vol. 5, 1907, p. 24. 

- The Girod electric steel furnace. Vol. 6, 1908, p. 428. 

Electrochemical Industry. Steel production in the electric furnace. Vol. 1, 1902, 
p. 247. 

Englehardt, V. Electric induction furnace for making steel. Electrochem. and 
Met. Ind., vol. 3, 1905, p. 294. 

- The induction furnace and its use in the steel industry. Electrochem. and 

Met. Ind., vol. 6, 1908, p. 143. 

Evans, J. W. Laboratory experiments on the electric smelting of iron ore. T. Can. 
Min. Inst., vol. 9, 1906, p. 128. 

Fitzgerald, F. A. J. The application of the Lash process to the electric furnace. 
Ann. Am. Electrochem. Soc, vol. 15, 1909, p. 149. 

- The Lash steel process and the electric furnace. Ann. Am. Electrochem. Soc., 

vol. 14, 1908, p. 239. 

Gin, G. Automatically circulating furnaces of the Gin type for the electrical produc¬ 
tion of steel. Trans. Faraday Soc., vol. 5, 1909, p. 137. 

• - Calculations of a Gin self-circulating induction steel furnace. Ann. Am. Elec¬ 

trochem. Soc., vol. 15, 1909, p. 215. 

• - Note on recent developments in the Gin electric steel furnace. Trans. Faraday 

Soc., vol. 2, 1906, p. 44. 

-— The new Gin process for the electrical manufacture of steel. Trans. Am. 

Electrochem. Soc., vol. 8, 1905, p. 105. 

-The self-circulating Gin furnace for the electric manufacture of steel. Trans. 

Am. Electrochem. Soc., vol. 15, 1909, p. 205. 

Girod, P. Studies in the electrometallurgy of ferro-alloys and steels. Trans. Faraday 
Soc., vol. 6, 1910, pp. 172-184. 

.—- The electric steel furnace in foundry practice. Met. and Chem. Eng., vol. 10, 

1912, p. 663. 

- The Girod electric furnace for the manufacture of steel. Trans. Am. Electro¬ 
chem. Soc., vol. 15, 1909, p. 127; Electrochem. and Met. Ind., vol. 7,1909, p. 259. 
Greene, A. E. Electric heating and the removal of phosphorus from iron. Trans. 
Am. Electrochem. Soc., vol. 22, 1912, p. 123. 

-Electric steel processes as competitors of the Bessemer and open hearth. 

Trans. Am. Electrochem. Soc., vol. 19, 1911, p. 233. 

Harbord, F. W. Recent developments in electric smelting in connection with iron 
and steel. Trans. Faraday Soc., vol. 1, 1905, p. 140. 

















204 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


Harden, J. A new electric furnace for steel melting and refining. Met. and Chem. 
Eng., vol. 9, 1911, p. 38. 

-Present status of the induction furnace, Met. and Chem. Eng., vol. 9, 1913, 

p. 99. 

- Recent developments of the Kjellin and Rochling-Rodenhauser electric in¬ 
duction furnaces. Trans. Faraday Soc., vol. 4, 1908, p. 120. 

- The “Paragon” electric furnace and recent developments in metallurgy. 

Met. and Chem. Eng., vol. 9, 1911, p. 595; Trans. Faraday Soc., vol. 7,1912, p. 183. 

Hering, C. Possible reduction of the power consumption in electric steel-refining 
furnaces. Met. and Chem. Eng., vol. 9, 1911, p. 590. 

Heroult, P. L. T. Electric steel process. Electrochem. Ind., vol. 1, 1903, p. 449. 

- Electric steel refining. Met. and Chem. Eng., vol. 10, 1912, p. 601. 

- The electrometallurgy of iron and steel. Trans. Am. Electrochem. Soc., 

vol. 6, 1904, p. 129. 

-The Heroult furnace. Electrochem. and Met. Ind., vol. 5, 1907, p. 411. 

Hibbard, H. L>. The present value of electrical structural steel. Trans. Am. Elec¬ 
trochem. Soc., vol. 15, 1909, p. 231. 

Izart, J. The Stassano furnace installed at the new works in Turin. Electrician, 
Oct. 12, 1907. 

Kearns, J. E. Electric annealing furnaces. Electrochem. and Met. Ind., vol. 4, 
1906, p. 95. 

Keeney, R. M. The production of steels and ferro-alloys directly from ore in the 
electric furnace. Jour. Iron and Steel Inst., Carnegie Scholarship Memoirs, 
vol. 4, 1912, p. 108. 

Keeney, R. M., and Lee, G. M. The direct production of steels and ferro-alloys 
from ore in the electric furnace. West. Chem. and Metal., vol. 6, 1910, pp. 269, 
323, 347. 

Keller, C. A. A contribution to the study of electric furnaces as applied to the 
manufacture of iron and steel. Trans. Am. Electrochem. Soc., vol. 15, 1909, p. 
87; Trans. Faraday Soc., vol. 5, 1909, p. 113. 

- Electrothermics of iron and steel. Trans. Faraday Soc., vol. 2, 1906, p. 36. 

Kershaw, J. B. C. Electric-furnace manufacture of steel. Iron Trade Rev., vol. 
51, 1912, pp. 865, 959, 1007, 1067, 1105, 1169. 

Kjellin, F. A. The Kjellin and Rochling-Rodenhauser electric furnace. Trans. 
Am. Electrochem. Soc., vol. 15, 1909, p. 173. 

Lee, G. M. See Keeney, R. M. 

Lipin, W. The Nathusius electric steel furnace. Met. and Chem. Eng., vol. 10, 
1912, p. 227. 

Lyman, J. The electric furnace for the manufacture of iron and steel. Trans. Am. 
Electrochem. Soc., vol. 19, 1910, p. 193. 

Metallurgical and Chemical Engineering. South Chicago electric-furnace plant 
of the United States Steel Corporation. Vol. 8, 1910, p. 179. 

- The electric furnace for small steel castings. Vol. 10, 1912, p. 54. 

Moldenke, R. Electric melting for the foundry. Electrochem. and Met. Ind., vol. 
5, 1907, p. 42. 

Mueller, A. The manufacture of steel in the Girod electric furnace. Met. and 
Chem. Eng., vol. 9, 1911, p. 581. 

Nathusius, H. Improvements in electric furnaces and their application in the 
manufacture of steel. Jour. Iron and Steel Inst., vol. 135, No. 1, 1912, p. 57. 

N eumann, B. Electric-furnace methods in iron and steel manufacture in comparison 
with the ordinary metallurgical processes. Electrochem. Ind., vol. 2,1914, p. 488. 

- Rochling-Rodenhauser induction furnace for three-phase currents. Elec¬ 
trochem. and Met. Ind., vol. 6, 1908, p. 458. 

Osborne, C. G. A few experiments with the 15-ton Heroult electric furnace at 
South Chicago. Trans. Am. Electrochem. Soc., vol. 19, 1911, p. 205. 











SELECTED BIBLIOGRAPHY. 


205 


Perkins, F. C. Rjellin electric furnace at Gysinge, Sweden, for the manufacture of 
steel. Electrochem. Ind., vol. 1, 1903, p. 576. 

Queneau, A. L. A new electric steel furnace. Trans. Am. Electrochem. Soc., vol 
17, 1910, p. 131. 

Richards, J. W. Metallurgical calculations; the electrometallurgy of iron and steel. 
Electrochem. and Met. Ind., vol. 5, 1907, p. 165. 

Pig steel made directly from ore in the electric furnace. Met. and Chem. 
Eng., vol. 10, 1912, p. 397. 

The electrothermic production of iron and steel, methods and furnaces. 
Jour. Franklin Inst., vol. 164, 1907, p. 443; vol. 165, 1908, p. 47. 

The electrometallurgical revolution in the iron and steel industry of Norway 
and Sweden. Proc. Eng. Soc. West. Pa., vol. 27, 1911, p. 125. 

- The Hiorth electric steel furnace. Trans. Am. Electrochem. Soc., vol. 18, 

1910, p. 191. 

- The largest electric steel works. Electrochem. and Met. Ind., vol. 7, 1909, 

p. 9. 

- The passing of crucible steel. Met. and Chem. Eng., vol. 8, 1910, p. 563. 

Robertson, T. D. The Gronwall steel-refining furnace. Met. and Chem. Eng., 
vol. 9, 1911, p. 573. 

Robinson, T. W. Electric steel-furnace experience at South Chicago. Met. and 
Chem. Eng., vol. 10, 1912, p. 372. 

Rodenhauser, W. The electric furnace and electric process of steel making. Jour. 

Iron and Steel Inst., vol. 79, 1909, No. 1, p. 261. 

Rowlands, T. Induction-furnace progress. Trans. Am. Electrochem. Soc., vol. 17, 
1910, p. 103. 

Stassano, E. Note on the rotating electric steel furnace in the artillery construction 
works, Turin. Trans. Faraday Soc., vol. 2, 1906, p. 150. 

- The application of the electric furnace to siderurgy. Trans. Am. Electrochem. 

Soc., vol. 15, 1909, p. 63. 

- Treatment of iron and steel in the electric furnace. Electrochem. and Met. 

Ind., vol. 6, 1908, p. 315. 

Stoughton, B. Notes on iron and steel and electrothermic manufacture of iron and 
steel. Jour. Franklin Inst., vol. 167, 1909, p. 73. 

Thallner, O. The manufacture of high-grade steel in the electric furnace. Electro¬ 
chem. and Met. Ind., vol. 6, 1908, p. 26. 

Turnball, R. The Heroult electric steel furnace. Trans. Am. Electrochem. Soc., 
vol. 15, 1909, p. 139; Electrochem. and Met. Ind., vol. 7, 1909, p. 260. 

Vom Baur, C. H. Electric induction and resistance furnaces for steel. Trans. Am. 
Electrochem. Soc., vol. 22, 1912, p. 117. 

-The Rochling-Rodenhauser furnace of the Crucible Steel Casting Co., Lans- 

downe, Pa. Iron Trade Rev., vol. 52, 1913, p. 153; Met. and Chem. Eng., vol. 
11, 1913, p. 113. 

Walker, W. R. Electric furnace as a possible means of producing an improved 
quality of steel. Met. and Chem. Eng., vol. 10, 1912, p. 371. 

Wedding, II. A modification of the induction furnace for steel refining. Electro¬ 
chem. and Met. Ind., vol. 6, 1908, p. 10. 

Wellman, S. I. Electric steel for rails. Met. and Chem. Eng., vol. 10, 1912, p. 372. 

TIN. 

Harden, J. Electric tin smelting. Met. and Chem. Eng., vol. 9, 1911, p. 453. 
Wile, R. S. An electric furnace for the treatment of tin dross, concentrates from 
cyanide mills, and other metallurgical works. Met. and Chem. Eng., vol. 10, 
1912, p. 495. 

_ Reduction of tin dross in an electric furnace. Trans. Am. Electrochem. 

Soc., vol. 18, 1910, p. 205. 












206 THE ELECTRIC FURNACE IN METALLURGICAL WORK. 


VACUUM AND HIGH-PRESSURE FURNACE. 

Arsem, W. C. Electric vacuum furnace installation in research laboratory of the 
General Electric Co. Ind. and Eng. Chem., vol. 2, 1910, p. 3. 

- The electric vacuum furnace. Trans. Am. Electrochem. Soc., vol. 9, 1906, 

p. 153. 

Fink, C. G. Electric vacuum furnace installation. Electrochem. and Met. Ind., 
vol. 4, 1906, p. 223; vol. 7, 1908, p. 428; vol. 8, 1909, p. 96. 

- Vacuum-furnace metallurgy. Trans. Am. Electrochem. Soc., vol. 21, 1912, 

p. 445. 

Hutton, R., and Petavel, M. Electric-furnace reactions under high pressure. 

Electrochem. and Met. Ind., vol. 6, 1908, p. 97. 

Petavel, M. See Hutton, R. 

ZINC AND LEAD. 

Betts, A. G. Electric lead smelting. Electrochem. and Met. Ind., vol. 4, 1906, 
p. 169. 

Bleecker, W. F. An electrolytic method for the reduction of blue powder. Trans. 

Am. Electrochem. Soc., vol. 21, 1912, p. 359. 

Brown, O. W. The reduction of metal sulphides. Trans. Am. Electrochem. Soc., 
vol. 9, 1906, p. 109. 

Brown, O. W., and Oesterle, W. F. The electric smelting of zinc. Trans. Am. 
Electrochem. Soc., vol. 8, 1905, p. 170. 

Engineering and Mining Journal. Electric zinc smelting. Vol. 94, 1912, p. 1109. 
Fitzgerald, F. A. J. A new electric resistance furnace. Trans. Am. Electrochem. 
Soc., vol. 19, 1911, p. 273; Met. and Chem. Eng., vol. 9, 1911, p. 259. 

- Note on an unsuccessful furnace experiment. Trans. Am. Electrochem. Soc., 

vol. 20, 1911, p. 281. 

Fleurville, E. Electric zinc smelting. Electrochem. and Met. Ind., vol. 7,1909, 
p. 468. 

Gin, G. The electrometallurgy of zinc. Trans. Am. Electrochem. Soc., vol. 12,1907, 
p. 117. 

Harbord. F. W. Zinc smelting at Trollhattan. Eng. and Min. Jour., vol. 93, 1912, 
p. 344. 

Ingalls, W. R. The electric smelting of zinc ore. Eng. and Min. Jour., vol. 94, 
1912, p. 7; Met. and Chem. Eng., vol. 10, 1912, p. 481; Trans. Can. Min. Inst., 
vol. 15, 1912, p. 101. 

Johnson, C. F. The electric zinc-smelting furnace. Met. and Chem. Eng., vol. 10, 

1912, p. 28. 

Johnson, W. McA. Notes on electric zinc smelting. Met. and Chem. Eng., vol. 
10, 1912, p. 537. 

- The art of electric zinc smelting. Trans. Am. Electrochem. Soc., vol. 24, 

1913, p. 191; Met. and Chem. Eng., vol. 11, 1913, p. 582. 

- The electrometallurgy of zinc and its relation to present practice. Trans. 

Am. Electrochem. Soc., vol. 17, 1910, p. 265. 

Keeney, R. M., and Lyon, D. A. Possible applications of the electric furnace to 
western metallurgy. Trans. Am. Electrochem. Soc., vol. 24, 1913, p. 119; Met. 
and Chem. Eng., vol. 11, 1913, p. 577. 

Kowalke, O. L. The volatility of zinc oxide. Trans. Am. Electrochem. Soc., vol. 
21, 1912, p. 557. 

Louvrier, F. Electric zinc smelting. Met. and Chem. Eng., vol. 11, 1913, p. 603. 

- Causes of the practical nonsuccess of the electric furnace in treating zinc ores. 

Met. and Chem. Eng., vol. 10, 1912, p. 747. 

Lyon, D. A. See Keeney, R. M. 








SELECTED BIBLIOGRAPHY. 207 

Metallurgical and Chemical Engineering. Editorial on the condensation prob¬ 
lem in electric-zinc smelting, vol. 10, 1912, p. 451. 

- Electric-zinc smelting in Norway and Sweden. Vol. 9, 1911, p. 673. 

Oesterle, W. F. See Brown, 0. W. 

Peterson, P. E. The electric-zinc furnace. Trans. Am. Electrochem. Soc., vol. 

24, 1913, p. 215; Met. and Chem. Eng., vol. 11, 1913, p. 583. 

Richards, J. W. The electric furnace in nonferrous metallurgy. Met. and Chem. 
Eng., vol. 8, 1910, p. 233. 

- The Johnson electric-zinc furnace. Trans. Am. Electrochem. Soc., vol. 19, 

1911, p. 311. 

Snyder, T. F. The condensation of zinc vapor from electric furnaces. Trans. Am. 

Electrochem. Soc., vol. 19,1911, p. 317; Met. and Chem. Eng., vol. 9,1911, p. 265. 
Vogel, J. L. F. The electrolysis of fused zinc chloride in cells heated externally. 
Trans. Faraday Soc., vol. 2, 1906, p. 56. 

Weeks, C. A. Melting nonferrous metals in an electric furnace. Met. and Chem. 
Eng., vol. 9, 1911, p. 363. 





PUBLICATIONS ON METALLURGY AND MINERAL 

TECHNOLOGY. 

A limited supply of the following publications of the Bureau of 
Mines is available for free distribution. Requests for all publications 
can not be granted, and applicants should select publications that 
may be of especial interest to them. Requests for copies should be 
addressed to the Director, Bureau of Mines. 

Bulletin 3. The coke industry of the United States as related to the foundry, by 
Richard Moldenke. 1910. 32 pp. 

Bulletin 8. The flow of heat through furnace walls, by W. T. Ray and Henry 
Kreisinger. 32 pp., 19 figs. 

Bulletin 12. Apparatus and methods for the sampling and analysis of furnace 
gases, by J. C. W. Frazer and E. J. Hoffman. 1911. 22 pp., 6 figs. 

Bulletin 47. Notes on mineral wastes, by C. L. Parsons. 1912. 44 pp. 

Bulletin 53. Mining and treatment of feldspar and kaolin in the southern Appa¬ 
lachian region, by A. S. Watts. 1913. 170 pp., 16 pis., 12 figs. 

Bulletin 54. Foundry cupola gases and temperatures, by A. W. Belden. 1913. 
29 pp., 3 pis., 16 figs. 

Bulletin 64. The titaniferous iron ores in the United States, their composition and 
economic value, by J. T. Singewald, jr. 1913. 145 pp., 16 pis., 3 figs. 

Bulletin 67. Electric furnaces for making iron and steel, by D. A. Lyon and R. M. 
Keeney. 1913. 142 pp., 36 figs. 

Bulletin 70. A preliminary report on uranium, radium, and vanadium, by R. B. 
Moore and K. L. Kithil. 1913. 100 pp., 2 pis., 2 figs. 

Bulletin 71. Fuller’s earth, by C. L. Parsons. 1913. 38 pp. 

Technical Paper 15. An electrolytic method of preventing corrosion of iron or 
steel, by J. K. Clement and L. Y. Walker. 1913. 19 pp., 10 figs. 

Technical Paper 31. Apparatus for the exact analysis of flue gas, by G. A. Burrell 
and F. M. Seibert. 1913. 12 pp., 1 fig. 

Technical Paper 41. The mining and treatment of lead and zinc ores in the Joplin 
district, Mo.; a preliminary report, by C. A. Wright. 1913. 43 pp., 5 figs. 

Technical Paper 60. The approximate melting points of some commercial copper 
alloys, by H. W. Gillett and A. B. Norton. 1913. 10 pp., 1 fig. 

208 


INDEX 


A. Page. 

Acheson, Edward, carborundum furnace of, 

details of. 9 

development of. 2 

figure showing. 9 

thermal efficiency of. 4 

graphite furnace of, details of. 8 

figure showing. 8 

thermal efficiency of. 4 

Acid-process.fumace, thermal efficiency of_ 4 

Albertville, Savoie, France, ferro-alloy plant 

at. 120 

Alby furnace, figure showing. Ill 

Alloys, electrical conductivity of. 188 

See also Ferro-alloys and various alloys 
named. 

Alumina, melting point of. 37 

Alumina brick, thermal conductivity of.39,40 

Aluminum, furnace for making, figure show¬ 
ing . 75 

types of. 75 

manufacture of, Bett’s process for.80,81 

Hall process for. 74 

H<5roult process for. 75 

price of. 140 

production of, in United States. 77 

specific gravity of. 76 

use of, as reducing agent. 134 

Aluminum industry, factors governing 

growth of. 78 

Aluminum silicates, production of aluminum 

from. 79,80 

Aluminum sulphide, reduction of. 81 

Alimdum as furnace lining. 34 

objections to. 34,35 

Alunite, deposits of. 78 

extraction of aluminum from. 78,79 

Ampere, definition of. 186 

relations of. 186 

Ampere-hour, definition of. 186 

Anode, requirements of, for electrolytic work . 27 

Apatite, as source of ferrophosphorus. 154 

Arc furnaces, classification of. 11 

See also Siemens furnace; Stassano furnace. 

Arsenic in ferrosilicon, effect of. 161 

Ashenary, on gases in ferrosilicon. 160 

Ashes, wood, thermal conductivity of. 40 

Austria, manufacture of ferrosilicon in. 155 

B. 

Basic-process furnace, thermal efficiency of... 4 

Baur, investigations of ferrochrome by. 127 

Bauxite, analysis of. 33 

melting point of. 37 

processes for purifying. 73,74 

production of aluminum from. 73,79 

use of, for furnace linings. 32,33 

Bayer process for purifying bauxite, details of. 73 


Page. 

Becket, F. M., on manufacture of ferro¬ 
chrome... 133,134 

on reduction of molybdenite. 149 

Behren, manufacture of ferro-alloys by. 132,180 

Benneville, production of tungsten alloys by. 180 

Berthier, manufacture of ferro-alloys by... 127,177 

Berzelius, manufacture of ferrosilicon by. 154 

Betts, method of, for production of aluminum 80,81 

Bibliography. 190-207 

Bier maim, production of ferrotungsten by. 177,181 
Blast furnace, manufacture of ferro-alloys in.. 103, 

135,142,143,163,164 

difficulties in use of.. 103 

results of. 143 

thermal efficiency of. 4 

Bonn, Germany, cost of electric power in fur¬ 
nace at. 70 

production of ferromanganese at. 103 

Bozel, France, ferrosilicon plant at, charge 

used in.164,165 

reducing agent used in. 165 

Braintree, England, electric furnace at, cost 

of electric power in. 70 

Brick dust, thermal conductivity of. 40 

Bridgewater, Pa., production of ferro-alloys at 106 

British thermal unit, relations of. 186 

Bunsen, reduction of aluminum by. 72 

Bureau of Mines, investigations of.84,91,101 

Burgess, C. F., classification of electric fur¬ 
naces by. 7 


C. 

Calcium in ferrosilicon, effect of.. 160 

Calcium carbide, manufacture of..124,125 

use of, as reducing agent. 133 

Calcium phosphide in ferrosilicon, effect of... 161 

use of, as reducing agent. 133 

Canada, manufacture of ferrosilicon in. 155 

Carbide furnace, development of.. 2 

electrode holders for, figures showing. 50-54 

Carbon, melting point of.. 37 

thermal conductivity of. 40 

use of, as reducing agent. 92, 

128,131,132,149,161,162 

for furnace linings.33,34 

See also Charcoal, Coal, Coke. 

Carbon monoxide, use of, in reduction of zinc 

oxide. 92 

Carborundum, composition of. 35 

melting point of. 37 

use of, for furnace linings. 35 

Carborundum furnace, details of. 9 

development of.. 2 

figure showing. 9 

thermal efficiency of. 4 

Carborundum sand, thermal conductivity of.. 39,40 
Carnot, manufacture of alloys by.. 132,155,156,180 
on composition of ferromanganese. 142 


\ 


209 






















































































210 


INDEX 


Page. 


Caron, experiments on ferrotungsten by. 177 

Cement, thermal conductivity of. 40 

"Centrifugal effect,” definition of.. 21 

influence of, on bath in furnace. 21 

Chalmot, manufacture of silicides of iron by.. 157 

Chaplet furnace, details of. 109 

figure showing. 109 

Charcoal, thermal conductivity of. 40 

use of, as reducing agent, relative advan¬ 
tages of. 83 

See also Carbon. 

Chromite, analysis of.34,128 

melting point of. 37 

smelting of, in electric furnace. 128 

use of, for furnace linings. 34 

Chromite ores, analyses of. 135 

Clinker, thermal conductivity of. 40 

Coal, anthracite, use of, as reducing agent.... 135 

Coke, powdered, thermal conductivity of.... 40 

use of, as reducing agent.81-84 

disadvantages of.82,83 

See also Carbon. 

Colemanite, analysis of. 126 

uso of. 126 

Combustion furnace, limitations of.2,3,6 

maximum temperature in. 6 

relative efficiency of. 3,4 

Conductivity, definition of. 188 

electrical, of metals and alloys. 188 

Conductors, list of. 188 

Conrad, W., ferrosilicon plant designed by... 166 

Copper, smelting of, in electric furnace. 87,88 

thermal conductivity of. 40 

use of, as conductor. 13,14 

Copper sulphate, electrolysis of, method used 

in.25,26 

Cote-Pierron, process of, for zinc smelting_ 92 

details of. 98 

Coulomb, definition of. 186 

relations of. 186 

Courtepin, Switzerland, ferro-alloy plant at.. 120 

Cowles, A. H., investigations of. 2 

smelting of zinc ores by. 91 

Cowles, E. H., investigations of. 2 

smelting of zinc ores by. 91 

Cowles process for reducing aluminum, de¬ 
tails of. 72,73 

Crawford, John, on electric furnaces in 

Sweden. 85 

on use of coke as reducing agent.82,83 

Crucible, proper volume of. 39 

shape of, factors governing. 30 

Crucible furnace, use of, in manufacture of 

ferro-alloys. 103,135 

Cryolite, melting point of, reduction of. 76 

specific gravity of. 76 

Crystolon as furnace lining. 35 

Cuba, chromite ore from, analysis of. 135 

Culley, ——, on resistance of water. 188 

Current, alternating, in ferro-alloy furnace, 

advantages of.22,117 

wave of, curve showing. 13 

direct, in ferro-alloy furnace, objections 

to. 117 

eddy, definition of. 18 

prevention of losses from. 18 


Page. 


Current, regulation of. 24 

self-induced, loss of power from. 18 

three-phase, types of connections for, fig¬ 
ure showing. 24 

D. 

De Laval, process of, for zinc smelting. 92 

Delta connections for single-phase furnaces, 

figure showing. 117 

Deville, reduction of aluminum by. 72 

Dinas brick, analysis of. 31 

characteristics of. 30,31 

Direct heating. See Heating. 

Domnarfvet, electrodes used in furnaces at .. 62 

Dunite, reduction of. 153 

Dupre, on gases in ferrosilicon. 160 


E. 

Eddy currents. See Current. 


Electric furnaces, advantages of. 2,3,6 

classification of. 7 

efficiency of, factors governing. 12-41 

energy required for, calculation of. 28 

internal dimensions of. 29 

limitations of. 5 ,6 

causes of. 5 , 6 

manufacture of ferro-alloys in. 104-106, 

143,144,164 

operation of, conditions governing.70,71 

output of, factors affecting. 27,28 

reduction of iron ores in. 84,85 

relative efficiency of. 3,4 

size of, relation of, to heat loss. 41 

smelting of copper ores in. 87,88 

relative advantages of. 89 

smelting of gold and silver ores in. 90 

voltage necessary in, factors governing... 29 

See also various furnaces named. 

Electrical connections for furnaces, figure 

showing. 114 

Electricity, cost of, conditions determining .. 67-69 

in metallurgy, history of. 2 

processes involved in use of. 1 

value of. 3 

methods of heating with. 13 

Electrode holders, construction of. 48,49 

figures showing. 107 , ill 

for carbide furnaces, description of. 50 

German, details of. 53 

figure showing. 58 

side, movable, details of. 55,56 

figures showing. 56-63 

use of. 48 

advantage of. 48 

top, types of. 50-54 

figures showing. 50-54 

use of. 47,48 

types of. 47,115,116 

water-cooled, details of. 52 

figures showing. 55,57 

with cooling device, figures showing.51,52 

Electrodes, arrangement of, in bundles. 62 

advantages of. 62,63 

block, holders for, figures showing. 60,61 

carbon, relative advantages of. 42 











































































































INDEX 


211 


Page. 


Electrodes, conductivity of, method of in¬ 
creasing .. 63 

connections for, figures showing. 63,64 

consumption of. 83,86,99,100 

current density of, conditions determin¬ 
ing. 61 

dimensions of, conditions determining... 60,61 

effect of use on, figure showing. 47 

efficiency of, conditions governing. 43 

figure showing. 107, 111 

graphite, relative advantages of. 42 

joining of, electrical losses caused by. 66 

methods of.65-67 

figure showing. 66 

loss of energy in. 42 

losses by, laws of.43,44 

manufacture of. 42 

properties of. 41 

round, holder for, description of. 52 

figure showing. 56 

size of, calculation of formulas for.45,46 

specially shaped, figure showing. 49 

thermal conductivity of, factors govern¬ 
ing. 43 

top holders for, use of.47,48 

types of. 42 

Electrolysis, application of, in electric furnace 

practice.25,26 

factors involved in. 26,27 

metal liberated by, calculation of. 26 

Electrolytes, preparation of, prerequisites of. 26 
Electro-Metals furnace, regulation of electric 

current in. 24 

Europe, growth of ferro-alloy industry in_ 105 


F. 


Farad, definition of. 186 

Faraday, investigations of ferrochrome by... 127 

Farup, P., on use of coke as reducing agent.. 82 

Ferberite, production of ferrotungsten from.. 178, 

179,181,183 

Ferro-alloy furnaces, current in. 117 

electrical connections in. 114 

electrode holders for, figure showing... 107, 111 

types of. 115,116 

essential details of. 113,115 

linings for. 115 

open-top, waste ofheatin. 116 

single phase, connections for, figure show¬ 
ing. 117 

three phase, connections for, figure showing 118 
Ferro-alloys, commercial production of, in 

electric furnace. 104 

definition of. 102 

kinds of. 103 

manufacture of, difficulties involved in.. 102 

electrode holder used in, details of.. 50 

figure showing. 54 

in blast furnace, difficulties in.103,104 

types of furnaces for. 106-118 

use of, in manufacture of iron and steel.. 102 

See also various ferro-alloys named. 


Ferro-aluminum, manufacture of. 125 

Ferro boron, composition of. 126 

manufacture of. 125,126 

production of, in United States. 106 


Page. 

Ferrochrome, analyses of. 138 

carbon-free, manufacture of. 135,137 

characteristics of. 132,133 

grades of. 133 

manufacture of. 103,104,119,124,125 

cost of. 1.39 

electrode consumption in. 138 

experiments in. 129-131 

furnaces used in. 135,136 

history of. 127 

materials used in. 128 

process of. 136,137 

price of. 140 

production of, in United States. 105,106 

refining of. 134,137 

cost of. 137 

uses of. 140,141 

Ferromanganese, manufacture of. 104,105 

experiments in. 103,142 

furnace used in. 143 

history of. 141,142 

process of. 142-143 

price of. 140 

production of, in United States. 105 

uses of. 144,145 

Ferromanganese-silicon, analyses of. 146 

grades of. 145 

manufacture of, methods of. 145 

price of. 145 

Ferromolybdenum, analyses of. 150 

characteristics of. 149 

elimination of sulphur from.147,148 

manufacture of, experiments in. 148 

history of. 146 

methods of. 147,150 

price of. 140 

production of, in United States. 106 

uses of... 150,151 

Ferronickel, analyses of. 152,154 

composition of. 151 

manufacture of. 151,153,154 

experiments in. 152 

production of, in United States. 106 

Ferrophosphorus, grades of. 154 

manufacture of. 154 

production of, in United States. 106 

Ferrosilico-aluminum, manufacture of. 175 

uses of. 175 

Ferrosilico-manganese-aluminum, grades of.. 175 

use of. 175 

Ferrosilicon, characteristics of. 158 

disintegration of, causes of. 158,160 

prevention of. 160 

formation of gases in, cause of. 158,160,161 

fusing point of. 159 

grades of, analyses of. 172 

classification of. 172 

manufacture of. 119,162,163 

charge used in. 164 

furnace used in. 106,107 

history of. 103,154,155 

in blast furnace. 163,164 

in electric furnace. 104,164 

reducing agents used in. 165 

variations in cost of. 173 

melting point of. 159 

















































































































212 


INDEX 


Page. 

Ferrosilicon, production of, in United States 105,106 


reduction of, with carbon. 161,162 

formula for. 161 

selling price of. 140 

silicon content of, effect of. 158 

specific gravity of. 158 

curves showing. 159 

transportation of, risks in. 173 

uses of.. 127,133,174 

Ferrosilicon furnace, changing of electrodes in. 169 

charges in. 170 

figure showing. 106 

labor required for. 171 

method of charging. 167,168 

power consumption of. 171 

slags in analyses of. 170 

formation of. 170 

tapping of. 169 

Ferrosilicon plant, details of. 166,167 

elevation of, figure showing. 168 

plan of, figure showing. 167 

Ferrotitanium, manufacture of. 175,176 

production of, in United States.105,106 

selling price of. 140 

uses of. 177 

Ferro tungsten, analyses of. 183 

manufacture of. 178,179 

experiments in. 180 

history of. 177 

processes of. 182,183 

reactions in. 181 

production of, in United States. 105,106 

selling price of. 140 

uses of. 1S4 

Ferro vanadium, analyses of. 185 

manufacture of, methods of. 184,185 

production of,in United States. 105,106 

selling price of. 140 

uses of. 185 

Fire brick, thermal conductivity of. 40 

Fire brick dust, heat conductivity of. 39 

Fire clay, melting point of. 37 

Fire-clay bricks, heat conductivity of. 39 

Fitzgerald, F. A. J., experiments by. 35 

on alundum furnace linings. 34,35 

on calcining of magnesia in electric fur¬ 
nace. 32 

on joining electrodes. 65 

France, production of ferro-alloys in. 155 

cost of. 139,173 

Fremy, manufacture of ferro-alloys by. 127,156 

Fulton, C. H., on composition of ganister ... 31 

Furnace linings, construction of. 115 

life of. 115 

Furnace walls, insulation of.39,40 

materials for, heat conductivities of. 39 

thickness of, conditions governing. 38 

relation of, to heat loss.40,41 

Furnaces. See various furnaces named. 

G. 

Ganister, composition of. 31 

Garnerite, reduction of.. 153 

Gas-engine power plants, cost of installing... 68 

operating cost of. 69 

Gas engines, electric power generated by, cost 

of. 68 


Page. 

Germany, manufacture of ferro-alloys in... 103,155 


selling price of ferro-alloys in. 140 

Gin, manufacture of ferro-alloys by. 134,156,181 

on charge of ferrosilicon. 164 

Girod, Paul, ferro-alloy plant of, figure show¬ 
ing. 121 

plan of. 121,122 

power supply of. 120,121 

production of. 122 

manufacture of ferro-alloys by. 120 

on value of boron. 126 

Girod furnace, details of. 110 

features of. 16 

figure showing. 16,110 

internal dimensions of. 29 

regulation of electric current in. 24 

Gold ores, smelting of, in electric furnace.... 90 

Goldschmidt thermit process, manufacture of 

ferrotitanium by. 176 

Goutal, manufacture of alloys by... 132,155,156,180 

on composition of ferromanganese. 142 

Graphite, thermal conductivity of. 40 

Greenwood crucible furnace, thermal effi¬ 
ciency of. 4 

Gronwall, experiments of. 2 

Guichard, M., manufacture of molybdenum 

by. 147 

Guillet, L., on composition of boron steel_ 126 

Giirtler, on cooling curves of iron-silicon sys¬ 
tem. 157 

on fusing point of ferrosilicon. 159 

H. 

Hadfield, use of ferrosilicon by. 174 

Ilagfors, Sweden, electric furnaces at, value of 

gas from. 86,87 

Hahe, on gases in ferrosilicon. 160 

on specific gravity of ferrosilicon. 158 

Hahn, manufacture of silicides of iron by.... 156 

Hall, C. M., investigations of. 2 

process of, for producing aluminum.73,74 

for purifying bauxite. 74 

Hansen, method of, for production of ferro- 

boron. 126 

Harbord, F. W., on zinc smelting in electric 

furnace. 93,95 

Hardanger, Norway, experiments at. 82 

Heat, development of, in conductor, relations 

of. 189 

waste of, in open-top furnaces. 116 

Heat loss, relation of, to size of furnace. 41 

to thickness of furnace walls. 41 

Heat unit, equivalents of. 187 

Heating, arc, method of. 16,17 

direct, by resistance, disadvantage of.... 13 

indirect-resistance, furnaces using.15,16 

method of. 15 

induction, definition of. 14 

factors governing. 13,14 

Helberger furnace, features of. 16 

figure showing.... 16 

Helfenstein furnace, details of. 118 

figure showing. 114 

Henry, definition of. 186 

Hering, C., laws of electrode losses by.43,44 















































































































INDEX. 


213 


Page. 


Hering, C., on insulation of furnace walls_ 39 

on measure of flow of heat. 44 

on “pinch effect”. 19 

on proper size of electrodes. 45, 46 

Herlienus, A., on quality of electric pig iron. . 86 

BAroult, Paul, investigations of. 2 

on increasing conductivity of electrodes.. 63 

process of, for manufacture of aluminum. 73,75 

Heroult, Cal., electric furnaces at, control of.. 25 

cost of power in. 70 

experiments in.82,83 

production of iron in. 84 

Heroult furnace, electrode holders for. 57 

figure showing. 10 

internal dimensions of. 29 

regulation of electric current in. 24 

Horsepower, equivalents of. 187 

relations of. 186 

Hubuerite, production of ferrotungsten from. 183 

Hutton, R. S., on reduction of aluminum 

oxides. 79,80 

Hydroelectric power, cost of installing, con¬ 
ditions determining. 67 

Hysteresis, definition of. 18 

I. 

Imbert-Thomson-Fitzgerald, process of, for 

zinc smelting. 92 

Indirect-resistance heating. See Heating. 
Induction furnace, bath of, cross section of, 

figure showing. 19 

disadvantages of. 15 

electromechanical forces in. 19 

elimination of pinch effect in.20,21 

essential features of... 15 

Induction heating. See Heating. 

Infusorial earth, thermal conductivity of.... 39,40 

Ingalls, W. R., experiments by. 96 

on life of retorts. 99 

Insulators, list of. 188 

Iron, smelting of, in electric furnace.84,85 

reducing agents used in. 81-84 

pig, in electric furnace, quality of.85,86 

thermal conductivity of. 40 

use of, in smelting zinc. 92,97,98 

Iron silicides, characteristics of. 156,157 

silicon content of, effect of. 157 

Iron-silicon system, cooling curves of, figure 

showing. 157 

Iron turnings, use of, in manufacture of ferro- 

silicon. 164 

J. 

Jacobs furnace, thermal efficiency of. 4 

Johnson, W. M., experiments by. 97 

process of, for zinc smelting. 92 

Joule, definition of. 186 

equivalents of. 187 

relations of. 186 

Joule’s law, statement of. 189 

K. 

Kaafjord, Norway, smelting of copper in elec¬ 
tric furnace at. 87 

Kanawha Falls, W. Va., furnaces at, charge 

used in. 165 

power consumption in. 138 

production of ferro-alloys in. 106 


Page. 

Kanolt, C. W., on melting points of fire bricks. 38 
Keeney, R. M., manufacture of ferro-alloys by 128, 

148,178,179 


on Swedish electric furnace. 85 

Keigelgen, use of silicon by. 133 

Keller, electrode connection designed by. 57 

advantages of. 59,60 

figure showing. 64 

manufacture of ferro-alloys by. 145 

Keller furnace, details of. 108,109 

figure showing. 108 

Kilowatt, equivalents of. 187 

relations of. 187 

Kjellin, experiments of. 2 

Kopperaaen, Norway, ferro-alloy furnace at, 

details of.111,112,122,123 

figure showing.111,112 

plan of.123,124 

power consumption in. 138 

power supply of.v. 123 

products of. 124 


L. 


La Praz, Savoie, France, cost of electric power 

in furnace at. 70 

Lag of current, definition of. 19 

Larsen, Alf-Sinding, method of, for reduction 

of aluminum. 80 

Lead ores, smelting of, in electric furnace.... 89,90 
Lebeau, production of silicides of iron by.... 156 

Lehner, W., results of experiments of. 147 

Lessing, electrode connection used by. 58 

Lime, as flux. 129 

as furnace lining. 32 

in reduction of molybdenite. 149 

melting point of. 37 

thermal conductivity of.39,40 

Lindblad, experiments of. 2 

Linings, for electric furnaces, neutral, kinds of 33-36 

refractories used in. 30 

Liquids, use of, as resistors. 10 

Livet, Isere, France, ferro-alloy plant at, 

charge used in.164,165 

cost of electric power in. 70 

plan of. 119 

power supply of. 118 

products of. 119 

reducing agents used in. 165 

Lloyd, on gases in ferrosilicon. 160 

Louis, J., electrode holder designed by. 55 

figure showing. 59 

on power consumption in production of 

ferrosilicon. 171 

M. 

McGill University, experiments at. 96 

Magnesia, calcined, thermal conductivity of.. 40 

electrically calcined, advantages of. 32 

melting point of. 37 

use of, for furnace linings. 32 

objections to. 32 

Magnesia brick, melting point of. 37 

thermal conductivity of.39,40 

Magnetic field, figure showing. 14 

Matthiessen, on resistance of German silver.. 188 

Meraker, Norway, cost of electric power in 

furnace at. 70 

































































































214 


INDEX 


Page. 


Metals, electrical conductivity of. 188 

See also various metals named. 

Mexico, smelting of gold and silver ores in 

plant in. 90 

Misselt, Wichelto, on thermal conductivity 

of insulating materials. 43 

Moissan, EL, investigations of. 16,104,128,132 

manufacture of ferro-alloys by. 147,155,156,180 
on temperature necessary for oxidation of 

carbon. 42 

Moissan furnace, description of. 16,17 

figure showing. 17 

Molybdenite, reduction of, experiments in... 148 

smelting of, methods of. 147 

Moulden, J. C., on smelting of zinc in electric 

furnace. 95 

Mushet, investigations of ferro-alloys by. 127 


N. 

Naske, manufacture of silicides of iron by.. 155-157 


Nathusius, electrode holder used by, figure 

showing. 63 

Neumann, G., investigations of. 127,147-149 

on production of aluminum. 74 

New Caledonia, chromite ores from, analysis 

of. 135 

New South Wales, analysis of chromite ores 

from. 135 

Newark, N. J., production of ferro-alloys at.. 106 

Niagara Falls, Canada, cost of electric power 

at. 70 

Niagara Falls, U. S., cost of electric power at. 70 

production of ferro-alloys at. 106 

Nickel, selling price of. 140 

Nickel silicide, composition of. 153 

manufacture of. 153 

Nonelectrolytic furnace, description of. 10 

Northrup, E. F., on "pinch effect”. 19 

Norway, manufacture of ferro-alloys in_124,155 

cost of. 139,173 

reducing agent used at ferro silicon 

plants in. 165 

Notodden, Norway, cost of electric power in 

furnace at. 70 

O. 

Odelberg, E., on quality of electric pig iron.. 86 

Oedquist, Gustaf, on use of coke as reducing 

agent. 82 

Ohm, definition of. 186 

Ohm’s law, explanation of. 189 

use of, in determining power factor.22,23 

Oil, crude, use of, as reducing agent. 84 

Olsen, H., on manufacture of aluminum. 74 

Osmond, F., manufacture of silicides of iron 

by. 156 

Output of electric furnace, factors affecting.. 27,28 

P. 


Patronite, use of, in manufacture of ferrovana- 

dium. 185 

Percy, investigations of ferrochrome by. 127 

Perkins, on increasing conductivity of elec¬ 
trodes. 64 


Page. 

Petavel, J. E., on reduction of aluminum 


oxides. 79,80 

Phalen, W . C., on experiments with alunite. 78 

on bauxite mining. 73 

Pick, W., design of ferrosilicon plant by. 166 

on manufacture of silicides of iron. 157 

Pig iron. See Iron. 

Pinch effect, difficulties caused by. 20 

elimination of, in induction furnaces.20,21 

influence of, on electric furnace. 20 

Pourcel, manufacture of ferro-alloys by-141,155 

Power factor, determination of. 22 

Price, E. F., on refining of ferrochrome. 134 

use of silicon as reducing agent by. 133 

Prieger, manufacture of ferromanganese by. 141,142 

Primos, Pa., production of ferro-alloys at_ 106 

Pyrrhotite, roasted, production of ferronickel 

from. 152 

Q. 

Quartz sand, thermal conductivity of.39,40 

Quartzite, use of, in manufacture of ferrosili¬ 
con. 165 


R. 

Reducing agents. See Aluminum, Calcium 
phosphide, Carbon, Charcoal, Coal, 
Coke, Ferrosilicon, Oil, Silicon. 


Refractories, acid, for furnace linings.30,31 

basic, for furnace linings, kinds of. 32 

for electric furnaces, selection of, condi¬ 
tions governing. 36-38 

thermal conductivity of. 40 

Remsheid, Germany, cost of electric power 

in furnace at. 70 

Resistance, electrical, laws of. 187 

of metals and alloys, variations in. 188 

specific, definition of. 188 

Resistivity, definition of.. 188 

Resistor, definition of. 7 

materials used as. 8 

Retort furnace, thermal efficiency of. 4 

Retorts, relative consumption of, in zinc 

smelting.99,100 

Reverberatory furnace, thermal efficiency of. 4 

Reynolds, experiments by. 97 

Rhodonite, as ore for making ferromanganese- 

silicon. 145 

Richards, J. W., on conductivity of alumi¬ 
num. 188 

on process for purifying bauxite. 73 

on thermal efficiency of zinc retort. 91 

Rigg, Gilbert, on properties of refractory 

materials. 36 

Rjukan, Norway, cost of electric power in 

furnace at. 70 

Rossi, A. J., manufacture of ferro-alloys by.. 175, 

176,181,182 

reducing agent for ferrochrome by. 134 

Rothenau, manufacture of ferrosilicon by.... 155 

Rumford Falls, Me., cost of electric power in 

furnace at. 70 

Rutile, cost of. 177 

use of, in manufacture of ferrotitanium.. 177 










































































INDEX 


215 


Page. 


St. Gervais, Switzerland, ferro-alloy plant at. 120 
St. Marcel, France, ferrosilicon plant at, 

charge used in. 165 

reducing agents used in. 165 

Sarpsborg, Norway, zinc smelting at, equip¬ 
ment for. 93 

results of. 94,95 

Sault Ste. Marie, results of experiments at. 151,152 

Schaller, experiments by. 78 

Scheelite, production of ferrotungsten from. 181,183 
Schilowski, J., experiments by, on smelting 

of copper ores. 88 

Self-induced currents. See Currents. 

Self-induction, definition of.. 18 

Series furnace, details of. 112 

figures showing. 112,113 

Serpek process for manufacturing aluminum, 

details of. 76,77 

Seward, use of silicon as reducing agent by.. 133 

Sheffield, England, cost of electric power in 

furnace at. 70 

Shelburne Falls, Mass., cost of electric power 

in furnace at. 70 

Siemens, William, investigations of. 2 

Siemens furnace, details of. 106,107 

figures showing. 12,106 

operation of. 107,108 

thermal efficiency of. 4 

Silica, melting point of. 37 

Silica brick, melting point of. 37 

thermal conductivity of. 40 

Silica sand, analysis of. 30 

Silicomanganese. See Ferromanganese-sili¬ 
con. 

Silico-spiegel, manufacture of. 155 

Silicon, in ferrosilicon, effect of. 158 

use of, as reducing agent. 133 

Silver ores, smelting of. 90 

Snake River, Idaho, cost of electric power at.. 70 

Snyder, F. T., on thermal conductivity of 

refractories. 40 

Solids, use of, as resistors. 8 ,9 

Spiegeleisen, definition of. 142 

Stalhane, experiments of. 2 

Stansfield, A., experiments by. 96 

on classification of electric furnaces. 7 

on heat conductivity of furnace materials. 39 

on heat loss in furnaces. 41 

on Moissan furnace. 16,17 

Stassano, E., experiments by.2,142 

manufacture of ferrotungsten by. 178 

Stassano furnace, electrode holder for, figure 

showing. 65 

figure showing. 11 

Steam turbine power plants, cost of installing. 68 

cost of operating. . 69 

Steel, chrome, characteristics of. 141 

manganese, characteristics of. 144,145 

uses of. 145 

manufacture of, use of ferrotungsten in.. 184 

tungsten, use of. 

turnings, use of, in manufacture of ferro¬ 
silicon. 164 

44713°—Bull. 77—16-15 


Page. 

Stephan, M., experiments of. 88 , 153,154 

Stodarts, investigations of ferrochrome by... 127 

Strohmayer, manufacture of ferrosilicon by.. 154 
Sulphur, elimination of, from ferromolyb- 

denum. 147,148 

Sweden, electric furnaces in, for production of 

iron. 85 

manufacture of ferrosilicon in. 155 ,165 

Switzerland, manufacture of ferrosilicon in... 155 

T. 


Tamman, on cooling curves of iron-silicon 

system. 157 

on fusing point of ferrosilicon. 159 

Temperature, effect of, on resistance of met¬ 
als. 188 

Thermit process for manufacture of ferro¬ 
chrome. 135,137 

Three-phase current. See Current. 

Tin, smelting of, in electric furnace. 101 

Tone, method of, for production of aluminum. 79,80 

Trollhattan, Sweden, furnace at, cost of elec¬ 
tric power in. 79 

electrodes used in. 62 

consumption of. 100 

results of experimental work in. 82,85,86,87 

smelting of lead ores in.89,90 

zinc smelting in. 93-95 

Trondhjem, Norway, smelting of copper in 

electric furnace at. 87 

Tube furnace, details of. 9 

figure showing. 9 

Tungsten, selling price of. 140 

Turkey, chromite ores from, analysis of. 135 

Turners Falls, Mass., cost of electric power in 

furnace at. 70 

Tyssedal, Hardanger, Norway, cost of electric 

power in furnace at. 70 


U. 


Ugine, Savoie, France, ferro-alloy plant at... 120 

charge used in. 164,165 

reducing agents used in. 165 

furnace at, cost of electric power in. 70 

United States, growth of ferro-alloy industry 

in. 105 

production of aluminum in. 77 

production of ferro-alloys in. 155 

cost of. 139,173 

selling price of ferro-alloys in. 140 


V. 


Valten, manufacture of ferrosilicon by. 154 

Van Linge, investigations of ferrochrome man¬ 
ufacture by. 132 

Van Norden, R. W., on electric control of fur¬ 
naces at Her oult, Cal. 25 

Vattier, copper-smelting experiments of.87,88 

Vogt, H. L., on use of coke as reducing 

agent. 82 

Volklingen, Germany, cost of electric power in 

furnace at. 70 

Volt, definition of. 186 



















































































216 


INDEX 


W. Page. 

* / 

Water, electrolysis of, method used in. 25 

Watt, definition of. 12,186 

equivalents of. 187 

relations of. 186 

value of, in measuring flow of heat. 44 

Wattmeter, use of. 23 

Webster, N. C., production of nickel alloys at. 153 

Weston, on resistance of German silver. 188 

Williams, manufacture of ferro-alloys by. 132, 

180,181 

Wilson, T. L., investigations of. 2,160 

Winteler, on aluminum cells. 74 


Wolframite, production of ferrotungsten from 178, 

181,183 


Page. 

Wolgodine, S., on conductivity of carbon and 

graphite. 42 

Wolkoff, W., experiments by, on smelting of 

copper ores. 88 

Z. 

Zinc, condensation of vapor from. 99 

smelting of, in electric furnace, methods 

of. 91,92,93 

difficulties met in. 99 

Zinc oxide, reduction of, method for. 96 

Zinc smelting, formation of blue powder in, 

causes of. 100 



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library of congress 































